drainage above ground...Above Ground Water Drainage Two main types 1. Single stack system 2....
Transcript of drainage above ground...Above Ground Water Drainage Two main types 1. Single stack system 2....
Drainage: Above ground
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Definition
• Above ground
– System of pipework required to carry waste fluids
and quasifluids away from appliances (e.g. sink,
washing machine, shower, toilet etc.) to
underground system
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Drainage terminology
• definitions
Waste water – sinks, showers, dishwashers etc.
Soil water – toilets.
Foul water – both waste and soil water.
Surface water – rainwater from roofs, roads etc.
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Functions of pipework
• Convey fluids or quasi-fluids from a to b.
• Control leakage inwards or outwards.
• Resist deposits of solids.
• Resist blockages.
• Resist abrasion by grit (scouring) esp. road drains.
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Functions of pipework.
• Resist corrosion by acid/alkali.
sulphate – bog/ chlorine – seawater.
• Accommodate pressure – internal/external.
– eliminate undue build up of gases.
• Allow access for maintenance
• Cost.
• Safety – asbestos link to lung cancer.
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Above Ground Water Drainage
Two main types
1. Single stack system 2. Two-pipe system
1.Single stack
• Most commonly used
• Soil and waste water discharge into a single pipe or stack
• Efficient working of the system is dependant on all branches (connections) being as short as possible and closely grouped on the stack
• Each appliance should be connected separately to the stack
• Stack should be vertical
• observe regulations for the diameter, length, fall and connections to the stack
Regulations for Single Stack
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Drainage
above
ground:
external
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Typical bathroom layout
Door
SVP
Design features • System should be
ventilated at every house or if the branch is longer than 6m.
• Access points should be placed at changes in invert level.
• Curves (where unavoidable) should have as large a radius as possible.
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cage
Min
900 mm
Above
Opening
If less
Than 3 m
From nearest
opening
Less than 3 m
Min . Centre line
Radius 200mm 100 mm min.
diameter
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Two-pipe System
• Older system is simple and effective.
• It has a soil pipe for the w.c. and a separate waste pipe for wash hand basins and baths.
• Allows flexibility in the placement of appliances but it is costly due to the amount of pipework.
Traps
• Trap is used at the connection of each appliance to the wastewater drainage system.
• Its purpose is to prevent foul odours entering the house.
• Trap is simply a water-sealed bend in the pipe work.
Traps A trap is used at the connection of each
appliance to the wastewater drainage system (e.g. sink). The purpose of the trap is to prevent foul smelling air entering the building.
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P’ trap Depth
of
seal
Water seal
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Traps
‘S’ trap
Water seal
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Traps Bottle trap
‘P’ outlet
Detachable bowl
Depth
of
seal
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When an appliance is emptied, the water flows away through the trap. However, the last portion of water is left behind in the trap creating a seal until the appliance is next used
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Plug
New water
Old water
Plug removed
Old water
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New water
forms seal.
Traps
How it Works
Siphonage
• The regulations with regards to size and placement of pipes in extremely important because of siphonage
• Siphonage is a difference in air pressure that creates suction.
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Siphonage
Self-siphonage
• Caused by the flow of water in the waste branch running full bore (across the entire diameter)and unsealing the trap by symphonic action
Induced siphonage
• The flow of passing water down the stack can cause suction in the waste pipe of the appliance, therefore unsealing the trap
Back Pressure/Compression
• Caused when the rate of flow of foul water is reduced suddenly due to a small radius bend
• Air then forces (by compression) the water in the trap back up into the appliances, breaking the seals