Syphonic Roof Drainage - Gebnorgebnor.com/pdf/GEBERIT/GeberitSyphonicsDesignGuide.pdfThe Geberit HDPE range of pipes and fittings accompanies the Pluvia outlets for total drainage

Syphonic Roof Drainage

Design Guide

Advanced Roof Drainage Technology

SYPHONICS

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Design, Manufacture and Installation

Millenium Plaza, Cardiff.

TSB Call Centre, Cardiff.

Honda Car Factory, Swindon.

The Light Office Block, Leeds.

The Lowery Galleria, Manchester.

Tesco, Old Swan.

Stoke City FC.

Geberit Pluvia is the leading syphonic

roof drainage system used throughout

the world.

Architects, Consultants and

Contractors have chosen the system

for some of the most prestigious and

ground breaking building designs due

to the freedom and flexibility it

provides.

Pluvia uses the ingenious gravity

induced vacuum principle to create a

syphonic action, which allows the

complete drainage of a roof area with

smaller diameter pipes than used in a

conventional gravity system.

Geberit Syphonic roof systems are

widely used in the industrial and

commercial sector for all roofs.

Geberit Pluvia Advantages

■ new architectural flexibility in

building and use

■ no slope in pipework required

■ less underground pipes

■ less sitework

■ fewer pipes and fittings

■ reduced pipe dimensions

■ less space required

■ self cleaning action

■ a simple and speedy fastening

system

The Geberit Pluvia System is fully approved by the BBA. This includes outlets, pipes &

fittings, and the dedicated design software.

All installations carry a minimum of a ten year product and design guarantee, and are carried out

by a Geberit Syphonics approved installer.

The product range includes outlets to suit most roof designs and finishes, with a comprehensive

range of contact foils to suit the majority of roof membrane materials currently on the market.

RIBA approved CPD seminars are available. Please contact Geberit for more information.

Conventional System

Fall 1 - 3 %

Many down pipes Fewer down pipes

Long underground pipes Short underground pipes

No fall necessary

Syphonic System

Design, Manufacture and Installation

1

2

Software

Geberit Pluvia DLS software

The highly advanced software package easily allows

the calculation of the most complex roof projects. It

offers distinct advantages:

■ convenient to operate

■ considerable time savings

■ very easy to use

■ provides

- Isometric drawings

- Hydraulic calculations

- Material list incl. fixing components

- Cost calculation with ready to mail tender

documents

The Geberit Pluvia Outlets are developed for all

types of roof structures. Due to the different discharge

rates of the outlets (6 l/s,

12 l/s or 25 l/s) an

economical layout of the

roof drainage system can

be reached. The wide

range of contact sheets

and accessories allows

connection to most roof

finishes.

The Geberit HDPE range of pipes and fittings

accompanies the Pluvia outlets for total drainage.

Geberit HDPE is available 40mm - 315mm, and can

be jointed in a variety of different methods including

electrofusion, butt

welding and

mechanical coupling.

The outstanding

material

characteristics of

Geberit HDPE allow

specifiers and

contractors to design

and pre-fabricate pipe runs away from the site of the

installation. Pipe runs can be created in a safe, clean

environment ensuring secure and accurate fabrication

as well as considerable material and labour savings.

The Geberit rail fixing system

The Geberit Pluvia fastening system was developed for

the installation of exposed, horizontal roof drainage

piping.

The expansion and contraction of the piping, which

occur after installation are absorbed by the system

itself. For this purpose, all mechanical forces are

transmitted to the square steel rail routed parallel to

the pipe.

Geberit rail fixing features

■ Large spans between beams can be bridged.

■ Fewer brackets on roof structures

■ Pre-assembly on the floor is possible:

- alignment of clamps on the rail, or

- alignment of clamps and of HDPE pipes on the rail

■ The clamps are conveniently secured with wedges.

■ Only very simple tools are required for the assembly

of the system.

■ The clearance required to install insulation against

condensation is accounted for in the design.

■ The system overcomes fixing constraints on

steel profile roofs.

■ The forces associated with changes in length as a

result of temperature fluctuations are absorbed by

the rail fastening.

Drawings and calculations

available from the Geberit

Technical Department or

Geberit Syphonic approved

installers.

Geberit Pluvia should only be installed by a Geberit

Syphonics approved installer.

3

Methodology for Designing a Pluvia System

Step 1Determine the roof(s) drainage patterns.

Step 2Calculate the areas of roof(s) draining to each outlet(see capacities on page 7)

Step 3Determine the rainfall intensity rate

Method AGeberit recommend using 108 mm/hr (0.03 l/s per sq.m.)

In the UK this figure provides a frequent return rate for a 2 minute storm which ensures the systems self cleansing routine is activated.

Method BUse the method and data provided in BS EN 12056 part 3. We do however advise against using the very high rainfall intensity rates that can be generated if long life spans for the building and high safety factors (categories) are used in the calculations.

Example:Project located in London requiring 25 year life span protection, Category 3 Safety Factor. This will result in a rainfall intensity rate of 236 mm per hour. In reality this will mean that once every 112.5 years for 2 minutes there may be a storm with a rainfall intensity of 236 mm/hour. Using this high rainfall rate will result in the systems pipework being massively oversized, which will result in the system not operating syphonically frequently, requiring a high level maintenance programme to check for silt build up in the pipes.

Geberit recommend using the rainfall rate mentioned in Method A and allowing any potential higher rate rainfall totemporarily accumulate on the roof (for valley gutters this may require some over sizing of the gutter to provideadditional storage capacity).

Example: If the 236 mm/hrs protection is required, design a primary system to cope with 108 mm/hr. The build up fromthe excess over 2 minutes would be 236

-108128 ÷ 30 = 4.3 mm

If the above mentioned temporary storage method is not acceptable then one of the three options below may be used:

Option 1Weir overflows in the parapet walls.

Option 2A secondary syphonic overflow system.

Option 3A separate internal overflow system (gravity). (See page 6 for detail)

In all roof designs an emergency/warning overflow must be provided to indicate a blockage within the system.

Step 4Contact the Geberit Technical Department or Geberit Syphonics approved installer to design and calculate a system.

4

Steel Profile Roof Deck(without Vapour Barrier Clamping unit)

Series 7 Outlet (12l/s capacity)

Electroweld Coupling and Brackets(Creating on Anchor Point)

Geberit Pluvia Rail System

Series 7 Outlet359.551.00.1

Roof Membrane

Thermal Insulation

Steel RoofProfile Decking

900 Bend

Vapour Barrier


Roof Membrane

Thermal Insulation

Vapour Barrier

Steel Gutter using a Clamping Ring

Geberit Clamping Ring359.568.00.1

Gutter


Steel Profile Roof Deck(with Vapour Barrier Clamping unit)



Steel RoofProfile Decking

900 Bend

Vapour BarrierClamped Seal Unit

Min 380 mm

Steel Gutter using a Contact Sheet/Foil

Flange to beriveted, solderedor weldeddepending ongutter finish

Gutter


Min. 350 mm

Typical Roof Types

Series 7 Outlet (12l/s capacity)

5

Concrete Roof (no Vapour Barrier)

Detail Showing Two Roof Finishes

Concrete Roof (with a Vapour Barrier)

Gravel


Paving


Roof Membrane

Insulation


Geberit Contact Sheetto be Bonded to RoofMembrane

Roof Membrane

Insulation



Concrete Slab

900 Bend

Promenade Outlet (with a Vapour Barrier) Timber Roof Construction



Roof Membrane

Insulation

Insulation

Series 7 Outlet359.550.00.1(Remove top grating


Promenade top359.635.00.1

Concrete Slab

900 Bend


50mm Ventilation Gap

Timber Joists

12mm Plasterboard


Timber RoofDeck

RoofMembrane



Concrete Slab

900 Bend

Vapour Barrier

Vapour BarrierPaved Area



Typical Roof Types

Detail Showing Two Roof Finishes

Gravel Paving

Remove and discardfunction disc fromoutlet

Adaptor* Ref: 6147/DVW

*Flow capacity of outlet withadaptor similar to standard outletbut with water depth 90mm(normal 40mm)

50mm high standpipe

Roof deck

Pushfit joint

Series 7 outletcover holds unitin place

Series 7 Overflow Adaptor

PVC Roof Finish

Geberit PVC Coated OutletFlange to be bonded toPVC Roof MembranePluvia Grating

Concrete Slab

Pluvia Outlet359.501.00.1*

*359.500.00.1Stainless Steel Finish

56

214

15mm max

Asphalt Roof Finish

PluviaGravel/ClampingRing 359.511.00.1 (Fixing extension Rodsand nuts extra240.816.00.1)

Pluvia Grating

ConcreteSlab

15mm Max

Mastic Asphalt

Pluvia Outlet359.500.00.1

56

214

Insulation

Stones or paving Slabs

90

280

Pluvia GratingHeld in place bya wing nut

Pluvia Outlet359.502.00.1

Concrete Slab

25 Litre Outlet

Geberit PVC CoatedOutlet Flange to bebonded to PVC RoofMembrane (This outlet isalso available without PVCcoating 359.573.00.1 forother roof finishes

6

Series 7+ Outlet (25l/s capacity)

Series 5 Outlets (6l/s capacity)

Typical Roof Types and Overflow

7

Technical Specification of Outlets

Series 5 Outlet (Small)

Min. flow capacity 1l/s +

Max. flow capacity 6l/s

Discharge capacity (outlet in gutter) 1-5l/s

Outlet spigot diameter 56mm

Standard Series 7 Outlet

Min. flow capacity 1l/s +


Discharge capacity (outlet in gutter) 1-10l/s


High Capacity Series 7+ Outlet

Min. flow capacity 8l/s


Discharge capacity (outlet in gutter) 20l/s


Design Parameters

Min. pipe diameter 40mm

Max. pipe diameter 315mm

Min. flow velocity 0.7m/s

Min. water to air ratio 60%

Max. negative pressure 40-160mm (PN4)* -800mbar

Max. negative pressure 200-315mm (PN3.2)* -450mbar

Max. negative pressure 200-315mm (PN4)* -800mbar

Min. 2 outlets to be installed on a system

Emergency warning overflows must be provided on all roofs

Pluvia outlets should be spaced no further than 20 metres apart

Pluvia outlets should be spaced no further than 10 metres from end of gutter

All horizontal pipes must be laid level (no gradient)

+ This equates to 33m2 based on 0.03l/s (108m/hr)

*PN4 denotes a thicker wall pipe

8

Geberit recommend that a maintenance programme is

always implemented on completion of the project.

The intervals between inspection will depend on the

location of the building. The maintenance programme

should include:-

Clearing of all outlets of any debris

or silt as shown in figure 1.

a Remove lid

b + c Remove function disc

d Rinse function disc with

water

e Wipe outlet with cloth

1 2 3

Check that no pipes connecting

to outlets are blocked with silt etc,

if blockages are found they can

be removed by using a water jet

through the outlet after removing

the top unit and function plate (a,

b & c in figure 1)

Ensure all outlets have gratings

and tops in place. Order spares

from Geberit if necessary.

Maintenance

a

b

b

Figure 1

c

d

e

Geberit Ltd.New Hythe Business ParkNew Hythe LaneAylesford, Kent ME207PJ

Other Geberit Syphonic literature available:■ Product and price guide

Other innovative products available within the Geberit Ltd. product portfolio include:■ Geberit Terrain UPVC & HDPE soil, waste and underground drainage systems■ Geberit Mepla water supply■ Geberit Terrain Rainwater Systems■ Geberit Duofix wall hung sanitaryware installation systems, WC and urinal

flushing systems, electronic washroom solutions and shower toilets

Please call 0700 4323748 or visit www.geberit.co.uk for more information.

Tel:+44 (0)1622 717811Fax:+44 (0)1622 716920www.geberit.co.uk

Registered office as postal addressRegistration Number 761885 SYPHONICS

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Documents

Syphonic Roof Drainage - Gebnorgebnor.com/pdf/GEBERIT/GeberitSyphonicsDesignGuide.pdfThe Geberit HDPE range of pipes and fittings accompanies the Pluvia outlets for total drainage