9
Frequently asked plumbing questions
1. why can’t i run all the fixtures into the 4-way riser under the floor waste and then run
the 100mm pipe to the
h
2
grO
.
answer:
The best greywater comes from the bath or shower because the volume of water is relatively
high compared to the amount of shampoo or soap. Conversely, water from the basin
contains lots of shaving stubble, shaving cream, tooth paste etc and very little water. It is
always best to run an individual pipe from the fixtures selected to the
H
2
grO
.
2. what is the smallest diameter dwv pipe that can be installed under the concrete slab?
answer:
Pipes downstream of the water seal of a gully trap or unvented branch drain, shall be no
smaller in diameter than 65mm.
(Reference AS/NZS 3500.2 – Clause 3.3.3)
3. what is the Maximum distance you can run un-vented 65mm & 50mm pipe?
answer:
A 65mm pipe can be run 10m. A 50mm pipe can be run 6m. For Fixtures with 40mm or
50mm outlets the discharge pipe can be increased in sized to 65mm using a level invert taper
immediately downstream of the fixture trap for the purpose of extending the length of the
fixture discharge pipe to 10m.
(Reference AS/NZS 3500.2 2003 –Clause 3.3.3, Table 4.1 and Appendix D)
4. what is the Maximum distance you can run vented 65mm & 50mm pipe?
answer:
There is no limit if the vent is installed in accordance with AS/NZS 3500.2 Section 7.5 clause
7.5.11. The length of the vented discharge pipe is only influenced by the available fall.
5. how is the length of the pipe measured?
answer:
The length of a discharge pipe is measured from the weir of the trap to the point of
connection to a Gully, Vented Drain or Stack. This measurement includes both horizontal and
vertical lengths.
(Reference AS/NZS 3500.2 –Clause 1.5 and figure 1.1)
6. can the outlet pipe from the
h
2
grO
unit cut into an existing vertical stack?
answer:
Yes. Providing the connection to the stack is 600mm above the base of the stack and the
connection is made with either 45º junctions or sweep junctions.
(Reference AS/NZS 3500.2 - Section 6, subsection 6.7, clause 6.7.2)
7. can the
h
2
grO
unit be used instead of an Org?
answer:
Yes. The lid is fitted with a “pop-out grate” to relieve surcharge and may be used as an
overflow relief gully provided it is installed so the top is 150mm below the overflow level of
the lowest fixture connected to the drain. In retrofit installations it is highly unlikely that the
H2grO will be fitted below the existing ORG.
