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RAINWATER HARVESTIN SYSTEM COMPONENTS
Ir Hj Ismail Abd RahmanCivil Engineering & Structural Branch
Public Works Department
RAINWATER HARVESTING SYSTEM
Roof Catchment: Roof SurfaceConveyance: gutter & RWDPFiltration: First Flush Diverter & Leaf FilterStorage: storage tankDistribution Pipe Purification: Sand Filter, Pumps (if required)Water Top up
COMPONENTS OF RWH
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RAINWATER HARVESTING SYSTEM
TYPICAL RWH SCHEMATIC
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RAINWATER HARVESTING COMPONENTS
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24 7
Conveyance Layoutfor Rainwater Harvesting System
Section of Conveyance Layoutfor Rainwater Harvesting System
Rounded Polyethylene Tank
RAINWATER HARVESTING SYSTEM
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RAINWATER HARVESTING SYSTEM
ROOF CATCHMENT
• The design approach for roof drainage is to determine the layout and catchment area
• Roof Coefficient (C) is different depend on the material
• Asbestos roof materials is not recommended• Lead materials in any form should not be used in
the system
RAINWATER HARVESTING SYSTEM
ROOF COEFFICIENCY• Roof Coefficient (C) is different depend on the
material
It is impossible to collect every drop of rain that falls.
Light rainfall will only wet the surface and then evaporate
Heavy rainfall can overflow from the gutter
More water loss if roof is flat
Roof material absorbs some water
Evaporation losses
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ROOF COEFFICIENCY
RAINWATER HARVESTING SYSTEM
CONVEYANCE
• Gutters are used to convey water from the roof to pipes to the RWH tank
• Gutter convey water through rain water down pipe (RWDP)• Rainwater may also collect from the surface via on site
detention system• Gutter and RWDP drawing refer to Architect detail
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RAINWATER HARVESTING SYSTEM
GUTTER & RWDP DESIGN
Gutter and RWDP sizing can be refer to Chapter 4 : MSMA 2nd Edition
Design approach is to determine the size of components based on the roof area and rainfall intensity
RAINWATER HARVESTING SYSTEM
GUTTER & RWDP DESIGN
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RAINWATER HARVESTING SYSTEM
LEAF FILTER
• Prevents debris from entering the rainwater harvesting tank
• Improves water quality
• Reduces tank maintenance
LEAF FILTER
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RAINWATER HARVESTING SYSTEM
FIRST FLUSH DIVERTER The first line of defense against these
contaminants getting into rainwater tank is a First Flush Diverter
Preventing the first water, which may contain roof contaminants (such as sediment, bird droppings, spiders, insects, mosquito eggs and debris), from entering the tank.
To improve water quality and reduce tank maintenance
FIRST FLUSH DIVERTER
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FIRST FLUSH DIVERTER
FIRST FLUSH DIVERTER
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RWH TANK
• Rainwater tanks may be provided to collect rainwater from roof and gutter systems.
• These tanks can be used to:
a) provide water for non potable uses
b) on-site detention storage
• Tank material can be type of :-
– HDPE
– Poly Tank
– Steel Tank
– FRP
– Reinforced Concrete
RWH TANK
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ABOVE GROUND RWH TANK
ABOVE GROUND RWH TANK
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RAINWATER HARVESTING SYSTEM
BELOW GROUND RWH TANK
UNDERGROUND OSD INTEGRATED WITH RWHS
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RAINWATER HARVESTING SYSTEM
GRAVITY FED SYSTEM
• water collected in storage tank and fed by gravity to the points of use
RAINWATER HARVESTING SYSTEM
INDIRECT FED SYSTEM• water collected in storage tank, pumped to
an elevated cistern and fed by gravity to the points of use
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RAINWATER HARVESTING SYSTEM
DIRECT PUMP SYSTEM
• water collected in storage tank and pumped directly to points of use
RAINWATER HARVESTIN SYSTEM
WATER BACKUP FROM MAIN SUPPLY
• Water backup from main supply/domestic tank shall take place whenever the rainwater tank is empty
• Shall equipped with one way non return valve system or
• The overflow pipe in the rainwater tank is located at least 225 mm lower from the inlet public supply
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RWH FILTER
• Rainwater filter improve the quality of the water by removing all the sediment , dirt etc.
• Can be separate from a tank – sand filter
• Can be installed underground – external filter
WATER FILTER (SAND FILTER)
Sand Filter will minimize the extent of dissolved chemicals from dust, pollution and roofing material
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SAND FILTER
The filter size shall be determined by flow rate of the rainwater intended uses (litre/hour)
EXTERNAL FILTER
External Filter function is to remove the sediment from entering into the tank
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PUMPS• Pumps needs to lift
rainwater from lower to higher level & boosting the pressure
• Type of pump suitable for various conditions of use – booster, submersible etc
• Pumps need to calculate the flow rate and pressure head required
• Pump size and specification shall refer to mechanical drawing
Thank You..
