The Rippleffect: water efficiency for business

Cost-effective water saving devices and practices - for commercial sites

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Cost-effective water saving devices and practices - for commercial sites

Summary

Most organisations take water for granted and few know exactly how much water they are using. Many sites are paying more in water and wastewater charges than they need to and can probably reduce their water consumption simply and inexpensively. This Good Practice Guide describes a range of cost-effective water saving devices and practices - some with payback periods of only a few days. It highlights the typical water savings that can be achieved for commercial applications and explains how to identify the most appropriate devices and practices for your site. The suggested actions are summarised in a comprehensive table, which includes an indication of the potential costs and payback period. The potential cost savings and other benefits of reducing water consumption are illustrated with examples. The Guide is aimed primarily at organisations using water mainly for domestic purposes, including:

■ offices; ■ retailers; ■ hotels; ■ leisure and community centres; ■ schools and universities; ■ hospitals; ■ small businesses.

The water saving practices and devices described in this Guide are intended to be implemented as part of a systematic water saving campaign. Such a campaign is described in Saving Money Through Resource Efficiency: Reducing Water Use.

Can your organisation afford to ignore the savings that could be achieved by following the advice given in this Guide? Organisations that adopt a systematic approach to water reduction typically achieve a 20 - 50% decrease in the amount of water used. By using less water, organisations save money not only on water supply costs but also on wastewater disposal charges.

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Contents 1 Introduction 1 1.1 How can this Guide help? 1 1.2 Carrying out a water use survey 2 1.3 Free services from WRAP 3 1.4 Water Technology List 3 2 Choosing water saving devices and practices 4 2.1 First considerations 4 2.2 Estimating potential savings 4 2.3 The impact of water savings on operating costs 5 2.4 Setting the project budget 6 2.5 Identifying appropriate water saving devices and practices 7 2.6 Identifying project costs 7 2.7 Worked example for a commercial site 7 3 Water saving devices and practices 11 3.1 General water use 11 3.2 Toilets 18 3.3 Sinks 21 3.4 Showers 23 3.5 Boilerhouse 23 3.6 Swimming pools 27 3.7 Catering 29 3.8 Gardening 31 3.9 Laboratories 32 3.10 Garages 32 4 Action plan 34 4.1 Other sources of information 35 Appendices 36 Appendix 1 A typical water saving campaign 36 Appendix 2 Estimating water heating costs 37 Appendix 3 Converting between systems of units 38

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1 - Introduction 1.1 How can this Guide help? All organisations use water, but few know how much water they use and how they could utilise this knowledge to help them save money by reducing this amount. Organisations that adopt a systematic approach to water reduction typically achieve a 20 - 50% decrease in the amount of water used. By using less water, organisations save money not only on water supply costs but also on wastewater disposal charges.

This Good Practice Guide describes a variety of cost-effective water saving projects with payback periods from a few days to over one year. The Guide is intended to help commercial organisations and institutions identify the most appropriate water saving devices and practices for specific equipment, processes or sites. This Guide is aimed primarily at organisations using water mainly for domestic purposes, including:

■ offices; ■ retailers; ■ hotels; ■ leisure and community centres; ■ schools and universities; ■ hospitals; ■ small businesses.

It is also applicable to non-process water use at industrial or manufacturing operations. Process water use at such sites is covered by a companion guide, Cost-effective water saving devices and practices - for industrial sites. Inclusion of specific water saving devices and practices in this Guide is not a recommendation for their universal implementation. Cost-effective application is often site-specific.

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Before adopting any water saving device or practice, organisations should: ■ evaluate the technical issues; ■ consider the health and safety implications, including carrying out a COSHH1

assessment (where appropriate); ■ examine the financial considerations.

To help, this Guide highlights other benefits and possible disadvantages which should be taken into account when selecting a water saving device. The identification and evaluation of cost-effective water saving devices and practices should be part of a wider water saving campaign. The phases and steps involved in a typical water saving campaign are indicated in Appendix 1 and in the Guide Tracking water use to cut costs.

1.2 Carrying out a water use survey Before beginning a water saving campaign, you should review your water and sewerage costs to make sure it is worth taking action. As a rule of thumb, reductions of 30% in water and sewerage bills are usually achievable at little or no cost for sites that have not previously tried to save water. As much as 50%, or more, might be achievable if projects with payback periods of up to two years are included. Before being able to identify how and where water can be saved, it is necessary to understand how, where and why water is used at each particular site. This can be achieved by carrying out a water use survey and developing a water balance for a site as described in Tracking water use to cut costs. A survey of water use and patterns of use typically reveals:

■ excessive or unnecessary use; ■ unknown use; ■ unauthorised use.

A survey of wastewater discharges and routes to sewer typically reveals: ■ clean water discharges direct to sewer; ■ unauthorised surface water discharges to sewer; ■ possible savings in sewerage charges.

Tracking water use to cut costs.also contains details of how to measure water flow. For those without a technical background, it is sometimes helpful to illustrate flow as detailed opposite, to give an indication of what water might be costing a company.

1 Control of Substances Hazardous to Health (COSHH) Regulations 2002.

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1.3 Free services from WRAP Water minimisation is one of the easiest ways of achieving cost savings. WRAP provides a number of free guides and tools to help you reduce your water use and stop your profits from going down the drain. For more information visit the Rippleffect: www.wrap.org.uk/rippleffect

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1.4 Water Technology List The Government’s Water Technology List (WTL) promotes products that encourage sustainable water use and rewards businesses for investing in them. You can contact WRAP to find out about the Enhanced Capital Allowance (ECA) scheme for sustainable water technologies and the WTL. ECAs allow businesses to write off 100% of investments in designated sustainable technologies and products (listed on the WTL) against tax in the first year of investment. All businesses that pay UK corporation or income tax are eligible for the tax allowance. Even if your organisation is not eligible for tax relief, the WTL provides a source of information about devices that help to minimise water use. For more information see www.eca-water.gov.uk or contact WRAP’s resource efficiency helpline on 0808 100 2040

Please note that the legislation mentioned within this publication was checked for accuracy in September 2005 before going to press. However, legislation is constantly changing and being updated. For information on current environmental legislation, please visit the Environment Agency website: www.environment-agency.gov.uk/business/default.aspx

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2 -Choosing water saving devices and practices 2.1 First considerations Before starting to identify and evaluate water saving devices and practices, it is important to agree:

■ a target for net savings based on a preliminary water use survey (see section 1.2);

■ payback periods for any water saving projects.

Appendix 1 contains a flow chart showing the steps involved in a typical water saving project. This chart will help you to implement a water reduction programme. The individual steps are simple but they must be carried out in order to produce the most cost-effective water saving system.

2.2 Estimating potential savings Once the water balance has been established and water use in each area of the site is understood, a water minimisation team can be assembled to start to identify water saving opportunities. Advice on the selection and management of waste minimisation teams is given in Resource Efficiency for Managers. As a rule of thumb, implementing some low-cost measures can save around 40% water use in washrooms. Fig 1 provides estimates of the significant annual losses from taps that are dripping or left running. For example, a failing washer worth about 50 pence can result in a progressive leak and can cost as much as £900/year in water and sewerage costs. The costs given in Fig 1 are intended for guidance only. They represent an average for the UK in 2004/05. Costs will vary depending on the water supplier (and/or sewerage undertaker) and customer tariff, and will be subject to annual review.

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2.3 The impact of water savings on operating costs Cost savings can arise from reductions in:

■ water use; ■ water treatment costs; ■ on-site water pumping and heating (energy costs); ■ wastewater discharge.

Two drops/Fig 1 Water losses from an open tap

Savings can also arise from: ■ a reduced requirement for additional capacity for water storage; ■ increased capacity without having to upgrade the water supply system; ■ reduced corrosion and improved working conditions through the elimination of

leaks.

2.4 Setting the project budget Once you have estimated the potential impact of water savings on overall operating costs, it is useful to work out how much money could reasonably be spent on the project. This will eliminate obvious non-starters. One simple way of doing this is to work out the Maximum Project Budget (MPB).

To achieve the required payback period, the overall capital and operating costs of any water saving project must be less than the MPB. Operating costs should also be low enough to remain attractive in the long-term. Your organisation may use other methods of financial appraisal to determine the viability of proposed projects. In such cases, it is best to seek advice from the finance department.

2.4.1 Worked example This worked example from a fictitious site illustrates the ‘project budget first’ approach. For the initial evaluation, it is assumed that implementing the water saving project in the washrooms would reduce water use by 40%. Table 1 shows the cost with and without the water saving project. Using 208 m3/year less water would reduce annual water and sewerage charges by £354. This is not money saved, as the costs have not yet been taken into account. To achieve a one-year payback, the MPB will be £354, ie, the combined capital and first year operating costs of the new water saving devices and practices must be less than £354.

Maximum Project Budget (£) = Calculated saving (£/year) Required payback period

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2.5 Identifying appropriate water saving devices and practices Once the water minimisation team has identified potentially attractive opportunities for saving water, then appropriate water saving devices and practices can be investigated. Water saving devices and practices for commercial sites are considered in section 3 and summarised in Table 7.

2.6 Identifying project costs Given the Maximum Project Budget (see section 2.4), the next step is to evaluate the costs associated with the necessary equipment. In practice, this may be an ongoing process as water savings and costs usually depend on the equipment selected. For accurate evaluation, it is best to obtain quotations for the equipment costs and estimated water savings from potential suppliers or installation contractors. You also need to allocate the costs of the initial water survey and management time.

■ Project costs occur in two stages: ■ Implementation:

design and project management;

equipment purchase;

installation and commissioning of all equipment and instrumentation;

disruption of work during installation and commissioning. ■ Operation:

employee training;

use and maintenance of utilities;

disposal of wastes from any treatment processes;

monitoring (including water quality);

reporting.

Appendix 2 outlines how to estimate water heating costs.

2.7 Worked example for a commercial site This example from a fictitious small hotel highlights the importance of evaluating possible water saving measures for their economic viability.

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A 20-bedroom hotel with a restaurant and a bar (open to non-residents) decided to investigate ways of reducing its water and sewerage bills. These are based on a charge of £1.72/m3 (79 pence/m3 water supply costs and 93 pence/m3 sewerage charges) of water used. The hotel management also decided to implement water saving projects for which the expected payback is less than two years.

8 Following a water use survey and brainstorming session to discuss ideas, the hotel management ruled out making changes to:

■ dishwashers and other washing machines as these are all new; ■ sinks used for food, glass and utensil washing as these require controlled flow; ■ baths and showers because these are relatively new.

However, it was discovered that: ■ bedroom washbasins are used much less frequently than others elsewhere in the

building (some of which are sometimes left running); ■ the flushing volume of the toilets with cisterns could be reduced from nine litres to

about seven litres; ■ a pair of urinals in the bar toilet share a cistern and could thus share a flush

control unit.

Tables 2 - 4 summarise the survey findings.

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The water saving team identified the following three possible water saving devices (see section 3):

■ fitting percussion (push) taps on all washbasins (50% reduction); ■ installing cistern volume adjusters in the WC toilets (16% reduction); ■ installing passive infrared flush controls in the urinal areas (typically 60 - 70%

reduction).

Table 5 shows the potential savings from installing these devices in the various areas of the hotel. When the project costs were compared with the expected savings, it was concluded that:

■ conversion to percussion taps on the washbasins was not cost-effective in this case;

■ fitting cistern bags to WC toilets was cost-effective; ■ fitting passive infrared control systems in urinal areas was cost-effective.

The estimated project economics are summarised in Table 6 overleaf. The total cost of the two water saving measures identified as cost-effective is £500. Savings of £781/year are predicted, giving an overall payback period of just under eight months.

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3 - Water saving devices and practices This section provides ideas on cost-effective devices and practices that can be used to reduce water consumption in general and for specific applications (toilets, sinks, showers, boilerhouses, swimming pools, catering, gardening, laboratories and garages). The advice is summarised in Table 7 and examples are given to illustrate the savings that can be made. Typical water use in office buildings is shown in Fig 2; around two-thirds is used in flushing toilets and urinals.

The key to a successful and effective water management programme is to find out how much water your site uses and how much it costs. To do this:

■ read (check) your water meter regularly (see section 3.1.1); ■ decipher and analyse your water bills - advice on how to do this is given in

Tracking water use to cut costs.

3.1 General water use This section should be read in conjunction with Table 7 overleaf.

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3.1.1 Taking meter readings

As part of the Rippleffect, you can download a simple, practical tool to enable you to record and monitor your water consumption. This series of Microsoft® Excel spreadsheets (monitoring_water_consumption.xls) is easy to use and allows you to record water consumption data and generate graphs automatically to illustrate trends. The data forms and graphs are designed for easy printing. To download the spreadsheets, go to http://www.wrap.org.uk/content/water-monitoring-tool-0

3.1.2 Leakage and overflows If water use is limited to daytime operations, it should be nearly zero during the night. Does this apply to your site? To find out, carry out a night flow test - read the meter when everyone has left and then again the following day before work starts. The meter reading should be the same. If it is not, you may have a leak or an overflow and further investigation is required.

Overflows are usually due to poor control and most run to drain without being measured. Leaks and overflows can arise from:

■ perished tap washers; ■ worn (cistern) valves; ■ corroded pipework; ■ flooded floats (balls) in water break tanks and cisterns.

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3.1.3 Isolation of water supply It is often hard to detect if an isolation valve (stopcock) (Fig 3) is open or closed and whether water is flowing through a pipe. Looking at the wheel, it is hard to know whether the valve is open or closed, ie is there flow in the pipeline or not? It is also impossible to judge the setting of such a valve when it is partially open. The installation of a quarter turn ball valve (Fig 4) provides a clear indication of whether the valve is open or closed.

■ When the lever is at right angles to the pipe (as shown), supply is switched off.

■ When the lever is in line with the pipe, supply is switched on. This also enables quick and effective isolation of the water supply. This can also be achieved using a simple isolator valve (see Fig 5).

An isolator valve is often installed on most modern washroom pipework.

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3.1.4 Water pressure High water pressure can:

■ result in excessive water consumption; ■ cause or exacerbate leakage; ■ put additional (unnecessary) wear and tear on the distribution system.

To meet minimum pressure and flow requirements, water mains are usually operated at a pressure of about 2 - 4 bar (200 - 400 kPa), though there is currently no stipulated maximum mains pressure limit. In some cases, higher water pressures than necessary may be delivered to the lower floors of tall buildings. This can occur where the water is supplied under gravity from a break tank in the roof void or where distribution systems are equipped with booster pumps to ensure adequate pressure is delivered to the top floors of tall buildings. This is illustrated by the following example. Example of overuse due to high pressure Compare the flow through an open tap on the top and ground floors of a 15-storey building with water being fed from a break tank on the roof. The flow through the tap on the top floor will be around 10 litres/minute, which is perfectly acceptable to the user. However, the tap on the ground floor will be flowing with considerable force at approximately 28 litres/minute, which is much more than necessary. Assume that the taps on the ground floor are used for handwashing (20 seconds per person) by 500 people-equivalents each day. This represents an overuse of around 3 m3/day or over 780 m3/year (assuming a five-day week). At an average combined water and sewerage charge of £1.72/m3, this represents a financial loss of around £1 340/year for this overuse of water alone. This does not include the energy cost associated with heating the water. Use of pressure-reducing valves Pressure-reducing valves or PRVs (see Fig 6) can be used to control the pressure in the incoming main or the distribution system. As well as being fitted on the incoming mains, PRVs can be installed on:

■ the supply to each floor; ■ the down legs of a gravity-fed distribution

system; ■ risers in a pumped system.

The valve can be preset or adjustable. PRVs can typically accept delivery pressures of up to 25 bar (2 500 kPa) and deliver a pressure of 1.5 - 6 bar (150 - 600 kPa) under variable flow conditions. They are available in a number of sizes; an adjustable PRV will cost around £20 (15 mm) to £200 (50 mm), excluding installation. When considering the use of PRVs, it is important to:

■ identify the minimum required operating pressure that will not compromise performance, ie that equipment will operate effectively with the new pressures;

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■ check that mixer taps or shower mixer units will not be affected adversely by the new pressures, ie the thermostatic control will still operate.

3.1.5 Flow regulation Many systems require preset water flow rates. The flow rate in such systems is usually adjusted by careful setting of a control valve. However, the same valve is often used to isolate the water supply and is not reset to the same position when flow resumes. A simple and cheap solution to this problem is to:

■ fit a quarter-turn isolation valve, eg ball valve (see Fig 4); ■ replace gate valves (see Fig 3) with quarter-turn isolation valves so that known

flow rates can be reset easily; ■ preset the existing flow control valve to the optimum flow rate; ■ remove the handwheel from the flow control valve to prevent unauthorised

changes to the flow rate.

Where a precise or high flow is not crucial (eg for general washing purposes), simple pipe restrictions can be used to limit the instantaneous flow from a device.

3.1.6 Reduce undesirable heat loss or gain ■ Do not run hot and cold pipes closely together in situations where the temperature

of the water is crucial to its suitability for use and water is used intermittently.

■ Lag pipework (or trace heat it) to reduce heat losses or heat gain (see Fig 7

overleaf). This avoids the practice of water being run to drain until it achieves the correct temperature. Lagging hot pipes will also reduce energy losses.

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imate determination of new flow rate, after a change in pressure:

New flow rate = Old flow rate New pressure Old pressure Chiller solves drinking water problem

2 For free advice and publications on energy efficiency, visit www.thecarbontrust.co.uk. ECAs are also available for the purchase of approved equipment on the Energy Technology List (www.eca.gov.uk).

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Lagging tanks and pipes will reduce heat losses and help maintain water at the required temperature.

3.2 Toilets Flush control is now required on new equipment under Water Supply (Water Fittings) Regulations 1999 (paragraph 25)

3 and the maximum flush of a WC pan limited to 6 litres.

Flush controls are now fitted as standard on urinals in new commercial buildings.

3.2.1 Flush control - urinals Urinals are often set to flush regardless of use. This wastes a lot of water - especially out of hours. Typically, uncontrolled flushing of urinals is set at three times an hour; a 7.5 - 12 litre cistern will therefore use 197 - 315 m3 water/year. Urinals must be flushed at the minimum frequency necessary to remain hygienic. When retrofitting flush controls in existing urinals, consult your supplier about the minimum flushing frequency desirable for your site’s specific circumstances. A number of devices can be used to control flush frequency. Hydraulic valve A hydraulic valve (pressure reducing valve - see section 3.1.4) can be fitted to the inlet pipework of the urinal system. When the inlet water pressure decreases temporarily through water being used elsewhere in the washroom (eg WC toilet flushing or hand washing), the diaphragm-operated valve opens, allowing a pre-set amount of water to pass to the urinal cistern. When the cistern is full, the auto-siphon will discharge and flush the urinal. When the washroom is not being used, the pressure remains unchanged and the valve remains closed. Passive infrared sensor A passive infrared (PIR) sensor can be installed in the washroom (see Fig 8) to detect use of the urinal facility. This sensor controls a solenoid valve to allow a pre-set amount of water into the cistern per use. When the cistern is full, the auto-siphon will discharge and flush the urinal. A PIR sensor costs about £120 and can be operated by battery (lifetime of 3 - 4 years) or mains electricity. During periods of non-use (ie out of hours), the device can be set to deliver a hygiene flush.

3 In England and Wales. The Water Byelaws 2000 apply in Scotland. For more information, contact the Water Regulations Advisory Service (www.wras.co.uk).

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Manual shut-off If work hours are predictable, a single valve such as a quarter turn ball valve (see Fig 4) can be installed in the pipework supplying the washroom. This can be closed manually each day by the last person to leave. Timer Alternatively, a timer can be installed on the pipework connected to the urinals such that water supplied to the cisterns is shut-off during periods of non-use. This is more flexible and reliable than the use of manual shutoff because it does not rely on someone remembering to switch off the water supply.

3.2.2 Flush volume - cisterns Cistern volume adjusters Flush volumes can be optimised by reducing the cistern size or by installing a cistern volume adjuster (CVA). There are a number of different types of CVAs available, which can be obtained from your water supplier at little or no cost. This simple device is either filled with or absorbs water (1.5 - 2 litres) once it is inserted in the cistern, thus reducing the volume of the cistern (see Fig 9). A CVA can reduce the volume of water used for each flush by up to 20%. However, each pan design has a minimum flushing volume and not all CVAs are appropriate for all types of cistern. Cistern dam A cistern dam works by retaining a proportion of the water in the cistern behind a ‘dam’ or partition, thus preventing this water from being discharged in the flush. The partition consists of a flexible synthetic compound that can be fitted between the front and back wall of the cistern. Dual flush A dual flush cistern operates a 6-litre flush for solid waste and a 4-litre flush for liquid waste. PIRs save over a million cubic metres of water per year Fig 9 Use of cistern bag

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Fig 8 Flush control using passive infrared sensor

3.2.3 Waterless urinals There are currently two types of waterless urinal - the siphonic trap and the deodorising pad. Siphonic trap A siphonic trap contains a barrier fluid that is inserted in the urinal bowl. The urine passes through the siphon and drains to sewer, while the low-density barrier fluid (a deodorising disinfectant) remains in the siphon. The disadvantages of this device include the need for;

■ specialised cleaning (cleaners must be advised of their use and maintenance procedure);

■ the addition of more barrier fluid every 1 - 2 weeks depending on use.

A retrofit siphonic trap costs about £90. Barrier fluid costs around £20 - £45 per urinal per year (2004/05 prices). Deodorising pad This device uses a pad impregnated with a deodorising chemical that is inserted in a modified S-bend to maintain hygiene. In most cases, the modified S-bend trap units are available as kits which can be retrofitted. Depending on use, the pads require changing once a week. Again, the disadvantage of this system is that it requires specialised cleaning (cleaners must be advised of their use and the correct maintenance procedure). Damage caused from objects (eg cigarette butts) blocking the waste pipe can be avoided by enclosing the pad in a chrome mesh case.

3.2.4 Waterless toilets There are several types of waterless toilet - composting, vacuum and incineration. Composting A large tank or composting chamber is installed below the toilet bowl to collect the waste. Liquid waste can be collected every couple of months, diluted and used as fertiliser for trees and flowers. The waste carries a hygiene risk and is not appropriate for use on fruit and vegetables. Solid waste is collected every couple of years and can also be used as fertiliser. The tank can be heated to increase composting and evaporation rates. This generates a smaller volume of waste and thus requires a smaller chamber. However, the use of electricity to provide the heat increases operating costs. Vacuum Vacuum toilets use air rather than water for flushing and require a vacuum tank, vacuum pump (often combined in one operating unit and referred to as a vacuum generator) and a holding tank (if discharge is not directly to sewer). They can be cost-effective if used on a large scale or in cases where conventional gravity drainage is a problem. The operation of a pedal opens a mechanical seal and allows a vacuum to draw the waste from the bowl. After the ‘flush’, the flap at the base of the pan closes and the vacuum pump continues to run until a vacuum has been re-established in the tank. Incineration

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A liner is dropped into toilet bowl before use. Pressing a foot pedal drops the waste and liner into an incineration chamber below the bowl where electrically powered heaters reduce the waste to ash. When cold, the ash can be disposed of with household refuse. However, the cost of the electricity to process the waste may outweigh the saving from reduced water costs.

3.2.5 Re-use of greywater

Greywater refers to wastewater from baths, showers and washbasins. Re-use applications include:

■ toilet flushing; ■ vehicle washing; ■ non-food crop irrigation.

However, care is needed when re-using greywater.

■ In most cases, greywater must undergo filtration and disinfection before use to prevent microbial growth and fouling of pipework.

■ Storage of greywater will encourage microbial growth, especially in warm weather.

■ It is not advisable to re-use water containing fats, oils and grease (FOGs) (ie wastewater from washing machines, dishwashers and kitchen sinks) because FOGs can clog pumps and membranes, and are hard to filter.

■ Care must be taken not to cross-contaminate greywater and mains water. A Type A air gap

4 should be installed between the mains inlet and the greywater header

tank. ■ Greywater pipework should be labelled clearly. ■ Maintenance is required every three months to check disinfection and filter

performance. If used, biological treatment (large-scale systems) requires additional maintenance.

The re-use of greywater is more cost-effective for larger sites. There is a lower health risk associated with using rainwater (see section 3.8.5) rather than greywater. For further information, see:

■ PR080 Rainwater and greywater use in buildings. Decision making for water conservation. ISBN 0860178803. CIRIA, 2001;

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■ C539 Rainwater and greywater use in buildings. Best practice guidance. ISBN 0860175391.CIRIA, 2001;

■ Technical Note TN 7/2001 Rainwater and greywater in buildings: project report and case studies. ISBN 0860225771. BSRIA, 2001.

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3.3 Sinks 3.3.1 Reduced bowl filling Does the sink need to be completely filled to use it? If not, consider:

■ using less water; ■ using a smaller sink; ■ specifying smaller wash bowls when fitting new installations.

4 An air gap of 20 mm between the inlet pipe and the header tank or twice the inlet bore diameter of the inlet pipe, whichever is greater. 5 Available from CIRIA Bookshop (Tel: 020 7549 3300; www.ciria.org.uk) 6 Available from BSRIA Bookshop (Tel: 01344 426511; www.bsria.co.uk)

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3.3.2 Taps Have you e ver forgotten to turn off a tap? A number of devices can automatically close taps or reduce flow through taps. Automatic taps Percussion or push taps (see Fig 10) are self-closing taps that close after operating for a preset time, thus eliminating the possibility of water being left running. Such taps have a cut-off mechanism which can be adjusted so that the water stops flowing in 1 - 30 seconds. Percussion taps cost around £20 each and can reduce water use by over 50%, compared with conventional taps. They can be supplied as kits, which simply fit onto existing standard tap bodies without the need to disrupt existing pipework connections.

Spray taps Spray taps work by forcing water through small holes in the tap outlet, thus producing a mist or spray. Spray taps can reduce water use by 60 - 70% compared with conventional taps. However, the spray head needs to be checked regularly for fouling from soap, grease and limescale. These devices are not recommended for areas of low use because the spray head can provide favourable conditions for legionella under such conditions. This is not the case when the taps are in frequent use.

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Passive infrared sensors The use of a PIR sensor to automatically start and stop flow through a tap works in the same way as the sensor for controlling urinal flush frequency (see section 3.2.1). Flow restriction All modern domestic pipework should be fitted with an isolator valve (see Fig 5). The valve can be used as a simple flow restrictor valve. When the adjustment slot is in line with the pipe, the valve is fully open. The adjustment slot can be turned to throttle the flow. However, should water pressure fall, the flow may no longer be adequate. In addition, a reduction in pipe diameter through the valve can easily become blocked in hard water areas. Foam soap Soap delivered as a foam or mousse from a dispenser provides good coverage and appears bulky. When users rub their hands together, the foam rapidly diminishes and requires little water to remove it. This generally means that less soap and water are used than with conventional liquid soap, giving a further cost saving.

3.4 Showers Typically, a conventional shower uses 35 litres (for a five-minute shower). However, power showers use substantially more water (70 litres or 12 litres/minute), which is often as much as a bath (70 litres). The amount of water used by a shower can be reduced by:

■ installing a flow restrictor in the pipework upstream of the shower fitting; ■ installing a flow restrictor in the shower head; ■ using a ‘water saver’ showerhead (this usually aerates the water or causes a fine

spray); ■ using a push button to control water use (commonly found in changing rooms,

schools and

leisure facilities).

3.5 Boilerhouse In larger commercial sites where there is a dedicated boilerhouse, significant quantities of water can be used in boilerhouse operations - for hot water supply, steam generation, heating, or a combination of these (see Fig 11 overleaf).

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24 The ‘value’ of this water is often underestimated as it may have already undergone several steps; each step adds to the ‘value’ or cost of the water. For example, the water may have:

■ been pre-treated (softening, demineralisation) before entering the boiler; ■ had conditioning chemicals added to it; ■ been heated.

Table 8 highlights the much higher cost of treated water, steam and condensate compared with that for potable water (ie water that is drinkable).

Not all water and steam is returned to the boiler for re-use. For example, losses occur through evaporation, use in the product, blowdown (see opposite) and poor condensate recovery. To compensate for these losses, fresh make-up water is added to the system, usually via the hot well. Installing a sub-meter on the inlet to the hot well will allow you to monitor the volume of make-up water. Measures to reduce water consumption in boilerhouse operations may also lead to significant energy savings.

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Fig 11 Boilerhouse operations

Pre-treatment Water is often pre-treated prior to its use in a boiler. Demineralisation or softening using ion exchange columns is common. These columns require regeneration (typically using hydrochloric acid/caustic soda for demineralisation plants and salt solution for softening plants), followed by a short period of operation to stabilise them. These processes use water and chemicals and generate wastewater. Regeneration of columns can be undertaken on one of the following bases:

■ daily (either manually operated or via a timer): this can be wasteful and expensive because regeneration is not related to column use;

■ volume of water treated: this can be wasteful and expensive if the quality of incoming water varies;

■ conductivity measurement: this is the most cost-effective method because regeneration is related directly to the quality of the treated water, ie the column is regenerated only when the total dissolved solids (TDS) set limit is reached.

Ideally, you should optimise the frequency of regeneration of the columns to minimise costs and environmental impact.

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Control of boiler blowdown Blowdown from the boiler purges the system of impurities, preventing a build-up of TDS in the boiler water. Boiler blowdown can be controlled manually through use of timers or conductivity measurements (typically linked to TDS). Automatic boiler blowdown control systems based on conductivity measurements are usually set to operate at a conductivity equivalent to a TDS of around 3 000 - 3 500 mg/litre. A typical treated water has a TDS concentration of 275 mg/litre.

Typically, boiler blowdown should be discharged to sewer and not to the surface water drain. Condensate recovery The condensate (hot water) derived from steam cooling has a value in terms of water and its energy content. Condensate occurs in steam lines and often at the point of use of the steam. Where possible, condensate should be collected and returned to the boiler hotwell, thus reducing the water and energy required to produce further steam and hot water. Since condensate does not require pre-treatment and is typically low in dissolved solids, its recovery for re-use reduces ion exchange costs and reduces blowdown requirements. Condensate is typically at 60 - 80°C, so the energy loss is also considerable. Steam losses and leaks The cost of generating and distributing steam is often underestimated

7. Steam contains a

significant energy content. To produce steam (at 100°C) requires the energy equivalent of heating water to around 650°C, ie around 80% of the energy input to a steam boiler is for the latent heat of vaporisation. Keep losses from leaks and poorly maintained steam vents to a minimum with regular checks, and prompt reporting and repair procedures.

7 See ECG066 Steam generation costs and ECG092 Steam distribution costs published by the Carbon Trust. See footnote above for the address of the Carbon Trust website.

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3.6 Swimming pools As shown in Fig 12 overleaf, water is used in a number of ways to operate and maintain a swimming pool, including:

■ fresh top-up water to replace evaporation losses from the surface of the pool; ■ backwashing of the sand filters; ■ pool and pool deck cleaning; ■ showers - customers are advised to shower before swimming (for hygiene

purposes) and usuallly shower after swimming too.

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The rate of evaporation from the surface of the pool depends on a number of factors, including:

■ the temperature of the water - ideally water temperature should be around 27 - 30°C;

■ the temperature of the air - if the air temperature is much higher than the water temperature, there is an increasing risk of condensation; if the air temperature is much lower than the water temperature, there is increased heat loss from the pool water through evaporation and convection;

■ the relative humidity in the pool hall; ■ the surface area of the pool; ■ the ventilation system.

Typically, mains water is used to top-up swimming pool water to replace losses from evaporation. Fitting a sub-meter to this system will allow you to monitor water use for this purpose. To optimise conditions:

■ keep the air temperature up to 1°C greater than that of the water, but no more than 30°C;

■ keep the relative humidity at around 50 - 70%; ■ install a pool cover when the pool is not in use. Covers also reduce ventilation

rates and the risk of condensation. Check covers regularly for deterioration.

Considerable amounts of water (often mains water - see Fig 12 opposite) are used for the backwashing of sand filters. Overuse of water is common.

■ Review requirements carefully to ensure water use is kept to a minimum without ■ compromising hygiene standards. ■ If possible, fit a sub-meter to the system to monitor water use and optimise the

operation.

An in-line monitoring system is often used to measure disinfection efficiency; a sample of water is taken, tested and then discharged to drain (see Fig 12). This can use significant amounts of water.

■ Review and optimise volumes used for sampling water for disinfection efficiency.

3.7 Catering Catering departments can be areas of high water consumption - particularly in those where food is prepared rather than cooked from chilled. In such cases, consider installing a sub-meter to the inlet of the kitchen(s) and, possibly, individual points of water use within the kitchen(s) to monitor and track water use. Water uses in catering operations include:

■ washing and preparing food; ■ washing food preparation areas and equipment; ■ cooking; ■ food waste disposal channels;

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■ dishwashers and glasswashers.

3.7.1 General The following measures will help to reduce general water use in catering operations.

■ Increase the awareness of the catering manager and staff of the value of water and the need to turn off taps.

■ Install taps which automatically shut off (ie foot-operated taps). ■ Fit spray heads (see section 3.3.2) or flow restrictors (see section 3.3.2) to taps

used for rinsing to reduce the maximum flow. ■ Review operations, eg:

- automatic potato peelers often require a water supply to flush out the waste peelings. Set the flow to the minimum necessary for satisfactory operation. A flow restriction device (see section 3.1.5) will ensure that this flow is not exceeded.

- where hoses are used to clean floors and large pieces of equipment, use a low-flow high pressure hose or a 1/2” (12.5 mm) rather than a 1” (25 mm) ‘conventional’ hose. In either case, fit the hose with a trigger nozzle or spray gun (see Fig 13 below) so that it shuts off automatically when the grip on the trigger is released.

■ Review scheduling so that food is defrosted on time rather than relying on the use of water for rapid defrosting.

3.7.2 Food waste disposal channels Food waste from returned plates and dishes is often scraped into a food disposal channel through which there is a constant flow of water to transport the waste to a macerator before flowing to sewer.

■ Ensure the water flow along thechannel occurs only when the channel is being used. This can either be controlled manually or by using a sensor such as a PIR (see section 3.2.1). Once activated (ie when food is sent down the channel), the sensor can be used to deliver water along the channel for a given time period.

■ Only use disposal channels when necessary. If only one channel is needed, then only use one

■ channel. ■ Evaluate alternative methods of collecting food waste:

- using bins; - using a mesh basket over a sink and disposing of the solid waste retained

in the basket to a bin.

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3.7.3 Dishwashers and glasswashers Washers can use considerable amounts of hot water, detergent and rinse aids.

■ Use washers only when fully loaded. ■ Optimise cycle times and temperatures. ■ When replacing old equipment, consider new models that are water and energy

efficient and which allow the user to adjust cycle times and temperatures. Ask your supplier or look for ‘ecolabels’.

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3.8 Gardening 3.8.1 Sprays/jets Incorrect settings on spray systems can result in inefficient spray patterns.

■ Review the design, control and location of sprays and jets to ensure that water is distributed evenly and over the correct area, and for the correct time.

3.8.2 Automatic supply shut-off A garden hose can use 1 m3 of water every hour. If the hose is hidden under a bush and forgotten, then at an average UK water supply cost

9 of around 79 pence/m3, this will cost

£19/day (continual use). A lightweight, trigger-operated spray gun costs about £25. The payback period in this case - allowing £15 for fitting - would be about two days.

3.8.3 Abandon grass watering Unless green lawns are essential, grass does not need to be watered regularly. Most areas of grass in the UK will recover to a respectable green colour during the autumn without any artificial watering during the summer. Only well-drained or shallow areas may not recover.

3.8.4 Minimise evaporation Evaporation from soil and plants can be minimised by:

■ watering in the cool of the evening; ■ subsurface watering with permeable pipes; ■ using bark or gravel mulches.

3.8.5 Rainwater collection Rainwater from guttering can be used untreated (after coarse filtering to remove leaf and other debris) on gardens or for vehicle cleaning. Minor modifications to downpipes may be required to divert rainwater to a suitable storage drum or tank. However, it is important to consider that:

■ attention should be given to diverting overflow back to the rainwater drain; ■ outside storage tanks may require heating (anti-frost control) during the winter; ■ diverting rainwater may be costly if a building is fitted with numerous downpipes;

8 For more information on ecolabels, visit www.defra.gov.uk/environment/consumerprod/ecolabel or www.mtprog.com (the website of Defra’s Market Transformation Programme). 9 Cost varies depending on supplier and customer tariff, and is subject to annual review.

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■ if the building has a limited roof area, the quantities of water collected will be low regardless of the level of rainfall;

■ rainfall is sporadic and this source of water should not be relied upon for the whole year.

A domestic-size water butt (220-litre capacity, fitted with a lid), plus stand and rain diverter kit costs around £60. A tap located at the base of the butt allows water to be drawn off or a hosepipe fitted. Rainwater can be used to flush toilets, but it is advisable to treat the water prior to use. Typically, this involves fine filtration (using a 1 mm screen) and disinfection. Unless quality can be guaranteed, a rainwater system should have its own distribution system to prevent possible contamination of mains water and ensure isolation of supply. As a consequence, installation and maintenance costs can be prohibitive. For further information, see:

■ PR080 Rainwater and greywater use in buildings. Decision making for water conservation. ISBN 0860178803. CIRIA, 2001

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■ C539 Rainwater and greywater use in buildings. Best practice guidance. ISBN 0860175391. CIRIA, 2001;

■ Technical Note TN 7/2001 Rainwater and greywater in buildings: project report and case studies. ISBN 0860225771. BSRIA, 2001.

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The re-use of greywater is described in section 3.2.5.

3.9 Laboratories 3.9.1 Condensers and vacuum pumps Condensers and ejector or jet vacuum pumps are typically connected to a tap and set to operate at full flow on a once-through basis. Because this water does not come into contact with the material being condensed or pumped, the wastewater is clean and could potentially be re-used.

■ When the condenser/pump is not in use, ensure that the water supply is switched off.

■ Use a closed loop system, ie recirculate the flow. A chiller or constant temperature water bath, which you may already have, may be required to prevent the water temperature rising.

■ Consider replacing the vacuum pump with a mechanical vacuum pump.

3.10 Garages Garages use considerable amounts of water for vehicle washing. In addition to general measures to maximise efficiency and prevent waste (see section 3.1 and Table 7), the use of greywater (see section 3.2.5) and rainwater (see section 3.8.5) for vehicle washing can reduce consumption of mains water. All garages should have an oil separator installed on their surface water drainage system to prevent pollution. Separators must be inspected regularly and cleaned as required.

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10 Available from CIRIA Bookshop (Tel: 020 7549 3300; www.ciria.org.uk

11Available from BSRIA Bookshop (Tel: 01344 426511; www.bsria.co.uk).

12 Guidance on oil separators is given in PPG03 Use and design of oil separators in surface water drainage systems published by the Environment Agency, SEPA and EHS (see section 4.1).

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Wastewater from vehicle and component washing may be contaminated with waxes, particulates, detergents and hydrocarbons. Such wastewater must be discharged to foul sewer and not to the surface water drain. Discharge to foul sewer requires authorisation by the appropriate sewerage undertaker and may require a trade effluent consent. Wash water can be collected, treated and recycled. Systems include:

■ partial reclamation - where recycled water is used for washing (typically 75% of total water use) and fresh water for rinsing;

■ total reclamation - where all water is recycled. This often requires filtration to remove waxes and oils.

A water reclamation system is necessary to remove contaminants and may include one or more of the following processes:

■ filtration; ■ wax removal (electroflocculation to break up wax); ■ sedimentation; ■ centrifugal separation; ■ reverse osmosis.

Typically, wash water is collected in an underground sump or interceptor allowing coarse solids to settle out. Finer particles are removed by centrifugal separation and finally the water is fed under gravity through an activated carbon filter to remove detergent and other organics. In some cases, reverse osmosis is used to produce a high-grade water for final rinsing.

NB all equipment attached to the mains water supply must be compliant with the Water

Supply (Water Fittings) Regulations 1999.ec

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4 - Action plan

Find out how much your company is paying in water and wastewater

charges.

Use the guidance provided on the Rippleffect.

Carry out a water use survey for your site - see Tracking water use to cut

costs.

Develop a water balance for your site.

Identify and agree a target for water saving.

Estimate potential savings from reducing water use and wastewater

generation.

Identify other benefits from saving water.

Decide how much is worth spending on water saving projects.

Identify and evaluate appropriate water saving devices and practices.

Identify project costs.

Consider the impact of the water saving measures on your particular

activity.

Implement cost-effective water saving devices and practices. Remember to

check on the Water Technology List for information about products that

encourage sustainable water use. See www.eca-water.gov.uk for details.

Identification and implementation of cost-effective water saving devices and practices should be carried out as part of a campaign to minimise water use and wastewater generation at your site. A systematic approach to waste minimisation is described in Saving Money Through Resource Efficiency: Reducing Water Use and the four phases of a typical water saving campaign are summarised in Appendix 1. If necessary, obtain help. WRAP offers a range of free services including:

■ free advice from WRAP experts through the helpline on a wide range of environmental issues, legislation and technology;

■ a variety of publications and tools to help you reduce water use and wastewater generation;

To find out more, visit www.wrap.org.uk or contact the helpline 0808 100 2040

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4.1 Other sources of information 4.1.1 WRAP publications Use the Business Resource Efficiency Hub (www.wrap.org.uk/brehub) to identify the most relevant publications for your requirements. Particularly useful publications include:

■ Water Minimisation in the Food and Drink Industry ■ Saving Money Through Resource Efficiency: Reducing Water Use ■ Reducing Your Water Consumption ■ Tracking Water Use to Cut Costs

4.1.2 Other publications Useful publications from the Environment Agency, Scottish Environment Protection Agency (SEPA) and the Northern Ireland Environment and Heritage Service (EHS) include:

■ Pollution Prevention Pays. Getting your site right: industrial and commercial pollution prevention, 2004.

■ A series of over 25 Pollution Prevention Guidance notes (PPGs). Each PPG is targeted at a particular sector or activity and provides advice on statutory responsibilities and good environmental practice.

The various PPGs are available on request from local offices or can be downloaded from either www.environment-agency.gov.uk/ppg or www.sepa.org.uk/guidance/ppg The Environment Agency also publishes a range of free literature relating to water conservation and demand management, including:

■ Waterwise: good for business and good for the environment, 2002; ■ Harvesting rainwater for domestic uses: an information guide, 2003; ■ A study of domestic greywater recycling, 2000.

To find out more, visit the Water Resources area of the Environment Agency website (www.environment-agency.gov.uk ).

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A typical water saving campaign A typical water saving campaign involves four phases. These are summarised in Fig A1.

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Appendices Fig A1 Four phases of a typical water saving campaign

Estimating water heating costs The power required to heat water is much easier to estimate than the overall project costs (see section 2.6). You need to know:

■ required temperature difference (°C); ■ flow rate (litres/second); ■ density (kg/m3); ■ heat capacity of the water (the heat capacity of clean water = 4.18 kJ/kg°C);

For clean water, Power requirement (kW) = Flow rate (1 kg/second) x Temperature difference (°C) x Heat capacity (kJ/kg°C) Because the density of clean water is 1 000 kg/m3, a flow rate of 1 litre/second of clean water is equivalent to a flow rate of 1 kg/second. Dirty water may have a different density and heat capacity compared with clean water. If necessary, this should be taken into account.

Energy (kWh) = Power (kW) xTime (hours) Heating cost = Energy (kWh) x Energy unit cost (pence/kWh) The unit cost of a kWh of heating (pence/kWh) is given on your utility bill. Details of how to estimate water pumping, cooling and treatment costs are given in Cost effective water saving devices and practices - for industrial sites.

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Converting between systems of units

For further i

www.wrap.org.uk/rippleffect