Rainwater Harvesting in a Drought Dan Behringer & Phyllis Muska Texas Master Naturalist Hill Country Chapter October 26, 2011

Why rainwater?

• Conserve water resources to help preserve water levels in the aquifer

• Superior water quality softer water means less detergent, no lime/calcium buildup on shower walls and appliances

• Plants and landscape prefer rainwater

• May be more dependable than a well

• Save money if using city water 30-50% of total water used by a typical home is for landscape watering

• Reduces volume of storm water during heavy rain events

• May lessen erosion from runoff

• No chemicals or additives necessary

• It tastes good!

What are the components of a Rainwater Harvesting system?

• Collection

• Conveyance

• Storage

• Treatment

System Components

• Collection Catchment surface: the collection surface from which rainfall runs off

• Conveyance from catchment surface Gutters, downspouts, and pipe channel water from the roof to the tank

• Storage One or more tanks

• Conveyance to point of use Delivery system gravity-fed or pumped to end use

• Treatment/purification

• • Initial filtration Leaf screens, first wash diverters, and roof washers remove debris and dust from the captured rainwater before it goes to the tank

• • For potable systems, filters, UV lights, and other methods make the water safe to drink

System Schematic

Catchment Surface #1

• Phase 1 550 sq ft garage 1996

Catchment Surface #2

• Phase 2 2000 sq ft house - 2001

Catchment Surface #3

• Phase 3 2003

• 2400 sq ft barn

Gutters and Downspouts

Gutters and Downspouts

Fiberglass Tanks with Food-Grade Liner

• Phase 1: 5,000 gal

• Phase 2: 10,000 gal

• Phase 3: 10,000 gal

• Tanks must be same height!

Polyethylene tanks

• Riverside Nature Center 5000 gallons

Metal tanks Pioneer tanks from Australia

First Wash System standing pipe

First Wash System rain barrel

First Wash System the Eliminator Cost ~$1200

First Wash System vortex filter

First Wash System Filtration box Fiberglass box with removable filters $600-$800

Floating Cistern Filter ~$450

Grundfos MQ pump ~$575

Filters

UV light

• Sanitron Ultraviolet S-37B

• UV disinfection to kill bacteria

• 12 gpm

• Built-in bulb cleaning apparatus

• ~$900

Pump, Filtration and UV Light ~$2000

Quick-Connect Valve

What happens if it doesnt rain?

• 1 rain -> 600 gallons for each 1000 sq ft collection surface, depending on efficiency

• 2500 sq ft house: 1500 gallons per inch of rain

• Add a barn and garage to the system to total 5000 sq ft = 3000 gallons with just 1 rain!

Its All About Storage . . .

• 2007: 45 of rain

• 135,000 gallons went through system

• Our annual usage: approximately 36,000 gallons

• So . . . almost 100,000 gallons got away!

• . . .

• 2011: 6 of rain over last 12 months

• May need to have water hauled in

. . . And timing

• Figure approximately 50-75 gallons per day per person

• For 2 people: 3000-4500 gallons/month requires an average of 1-1 rain/month

• 25,000 gallons = 7-8 month supply

• 1996 summer 2011: never below a two-month supply

• To calculate capacity needed, figure on historic maximum number of days with no rain

How pure is the water? Is it really OK to drink?

• 5-micron spin filter

• 3-micron charcoal filter

• UV light

• Tests almost the same as distilled water

• pH around 6.0

• Tests available through UGRA, LCRA

Summer 2009 UTHSC Study

Costs

• Rough estimate for 20,000 gallon system, 2000 sq ft footprint, potable water:

• • Two fiberglass, polyester resin-lined 10K tanks @ $7,500: $15,000

• • Or one metal Pioneer tank 20K: $12,000

• • Gutters and downspouts: $500

• • First wash: $600-1500 per inlet

• • Pump: $600

• • Filtration and UV: $1000

• • Total: $15,000-$20,000 + delivery + labor comparable to drilling a well in many areas

Maintenance

• Change filters monthly/quarterly ~$100/yr

• Clean gutters as needed 1-2 times/year

• Replace UV bulb every 12-14 months ~$80-$100

Its Catching On . . .

• Recent survey by TRCA data from over 1,000 systems with total capacity of over 15,000,000 gallons

• More than 6,000 rain barrels were installed through the City of Austins incentive program from 1995-2005

• More than 100,000 residential systems in the US installed by professionals

• Countless do-it-yourself systems in place

• Kroc Center in Kerrville 135,000 gallons

• Boerne Champion High School

• Willow City Volunteer Fire Department 24,000 gallon system: gravity flow dispensing system can fill a 400-gal tank on a brush truck in 2 minutes

• Riverside Nature Center 5,000 gallon system collecting off ~4500 sq ft takes only a 2 rain to fill

• Menard Library with demonstration gardens

• Lady Bird Johnson Wildflower Center in Austin 70,000 gallons

Commercial applications

Non-potable applications

• Collecting water for irrigation purposes: can be as simple as running a hose from a downspout to a rain barrel

Non-potable applications

• Rain pillow 1000+ gallons stored in a bladder under the deck

10' x 8' x 2' tall (when filled) 1000 gallons ~$2500

Non-potable applications

• Guzzler watering station for wildlife and/or livestock

Water Conservation

• Key to preserving our precious water resources

• Cultivate a mindset for conservation until it becomes second nature use, re-use, then use again!

• Pay special attention to these guzzlers:

• • Toilets

• • Appliances

• • Landscape watering

• • Sprinkler systems

• Avoid bare dirt prevent runoff and erosion

• Landscaping: use native grasses, shrubs, forbs

• Collect condensate from A/C

Additional Resources

• http://www.twdb.state.tx.us/iwt/rainwater.asp

• http://www.greenbuilder.com/sourcebook/Rainwater.html

• http://www.rainwatercollection.com

Taste test

• Have a sample of our cloud juice fill your water bottle!