Drainage system regulations in New Zealand
In New Zealand, drainage system features such as gully traps and underground drains need to comply with requirements and standards set by Standards New Zealand, which is a unit within the Ministry of Business, Innovation and Employment.
A gully trap is a basin in the ground that receives piped wasterwater from your property before it enters the underground sewer. A gully trap can receive discharge pipes from several outlets.
Each residential building in New Zealand is required to have at least one gully trap. This is to ensure that if a drainage system becomes blocked, the gully trap provides the point where sewage can overflow outside the building, instead of building up wastewater in the pipe and overflowing inside the building.
Gully traps in New Zealand must:
- have an overflow rim of at least 150 mm below the overflow level of the lowest fixture served by the drainage system
- be located within the legal boundaries of the land on which the building stands
- prevent surface water from entering the trap
- be constructed so the grate will lift to allow surcharge
- have at least one discharge pipe feeding into it to maintain the water seal.
A floor waste gully acts as a floor drain as well as receiving the discharge from wastewater fixtures. It may only receive discharge pipes from wastewater fixtures that are located in the same room. It may also be used as a shower outlet but cannot receive solid waste.
The advantage of using a floor waste gully is that it reduces the number of connections required to the drain and the length of pipe.
They may be used in buildings where overflowing water could enter another property.
Ventilation of drains
Drainage systems must be ventilated to reduce the build-up of foul air within the drains.
A discharge stack that is within 10 m of the head of the drain may be used as the drain vent pipe.
Ventilation requirements of drainage systems are that:
- every drain must be ventilated by an 80 mm diameter minimum vent pipe which terminates to open air
- every branch drain over 10 m in length must be ventilated
- vent pipes must be located so that there is less than 10 m of upstream drain
- vent pipes must be located downstream of the discharge pipe that is closest to the head of the drain – to allow for regular flushing at the point where the vent connects with the drain.
Drainage Pipe Material
Drainage pipes need to have flexible joints so that pipes are not damaged by differential settlement.
Testing of drains
Drains must not be covered over until they have been inspected and tested for leaks.
Depending on the type of drain and the situation, tests that may be applied to a drain to test the joint performance include:
- water test
- smoke test
- coloured water test
- low-pressure air test.
This content was sourced from http://www.level.org.nz/. You can read the full article here – http://www.level.org.nz/water/wastewater/drainage-systems/
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