When Does a Wet Well Need to be Installed Internally?
It is not uncommon for the Plumber to be confronted with the challenge of connecting sanitary plumbing fixtures where they are to be located below the level of the Utility providers’ gravity sewer. This may involve the collecting and pumping of the combined black and grey water waste from multiple fixtures including whole of house or granny flat-type installations.
A ‘wet well’ is defined under AS/NZS 3500.0 as ‘a below-ground chamber for the collection of sewage and/or wastewater and fitted with a pumping device to raise the contents to a suitable disposal point’. This type of installation is common place in commercial projects however, there appears to be some confusion regarding a ‘wet well’ being approved to be installed in a domestic application particularly where such a facility would need to be installed internally such as in a basement.
A ‘wet well’ can be installed internally in a basement of a Class1a dwelling subject to any limitations stated in the NCC, AS/NZS 3500.2:2018 and the Queensland Plumbing and Waste Water Code.
The installation shall be subject to the following:
- The Installation shall comply with AS/NZS 3500.2:2018, Section 12 , Clauses, 12.5 and 12.6
- The outlet pipe from the sanitary pump shall discharge to an approved connection point in accordance with Clause 12.7
- The pump discharge pipe shall comply with the relevant sections of AS/NZS 3500.1:2018 and AS/NZS 3500.2:2018.
- The sanitary drainage system upstream of the ‘wet well’ shall be vented in accordance with AS/NZS 3500.2:2018 Clause 3.9 and shall incorporate provision for overflow relief in accordance with Clause 4.6.6.
The pumped discharge downstream of the wet well shall be protected from potential sewer surcharge in accordance with Clause 4.5 where the installation conditions necessitates such protection.
Before installing of a wet well we recommend that you consult with the relative Local Authority regarding any specific local specifications that may need approval. Furthermore, consideration should be given to the provision for alternative sanitary facilities in the event of power outages.
