Try the Sizing plumbing systems activity.
Sizing plumbing system components
We will now look in more detail at sizing plumbing system components:
- discharge pipes
- floor waste gullies
A fixture discharge pipe is the pipe from a single fixture.
Table 6.1, 'Fixture unit ratings', in AS/NZS 3500.2:2003 gives the minimum size of fixture discharge pipes for common fixtures.
A slop hopper requires a fixture discharge pipe size of DN 100. A water closet pan may have a fixture discharge pipe size of DN 80 or DN 100.
While floor waste gullies are deemed a fixture trap, the minimum size of the outlet pipe is determined according to Table 4.6, 'Floor waste gully outlet', in AS/NZS 3500.2:2003.
A maximum of 10 fixture units (including the discharge from no more than one bath) may be discharged to a floor waste gully with an outlet size DN 65.
The size of drainage vents is determined differently for different sanitary plumbing systems. Always ensure that you are reading from the correct section in AS/NZS 3500.2:2003 when determining the size of a vent in a particular system of sanitary plumbing.
To determine the vent size for a fully modified vented system, you should refer to Section 7.5 of AS/NZS 3500.2:2003.
Clause 3.9.3 in AS/NZS 3500.2:2003 provides information on sizing drainage vents. You must also refer to Table 3.5 in the same section.
While the main upstream drainage vent must be extended to open air, you may need to terminate vents above ground in the building to ventilate branches in the sanitary drainage system. This occurs where:
- lengths of branch drain below ground exceed 10 metres (Clause 3.10)
- lengths of branch pipe in 'Elevated pipework' exceed 10 metres (Clauses 3.10 and 9.12).
In these situations, air admittance valves (AAVs) may be installed and terminated above ground in the building. AAVs are sized in accordance with Clause 6.9.