Water use, sustainability, and efficiency by choosing quality systems and materials, and providing environmentally friendly solutions.


With wastewater, the overriding consideration is building users’ health and safety.

Most buildings will connect to a town or city sewerage system – where a sewerage system is available, connecting to it is compulsory under Building Code clause G13 Foul water. However, there are options for on-site disposal that can be used when there is no mains sewerage available. Some wastewater can also be recycled for use in garden irrigation or (with appropriate filtration and treatment) toilet flushing or other purposes.

In this section, we describe best practice options for installing standard wastewater systems. We also describe other options such as greywater recycling.

While recycling greywater has benefits, maintenance is required to keep these recycling systems operating properly. Specific maintenance tasks should be pointed out to clients considering this option, without discouraging them, before they make a final decision.

Code requirements

Installation of sanitary plumbing and drainage systems in New Zealand must be in accordance with NZ Building Code clause G13 Foul water or AS/NZS 3500 Plumbing and drainage.

The key objectives of Clause G13 are to safeguard people from:

  • illness due to infection or contamination as a result of personal hygiene activities
  • loss of amenity due to the presence of unpleasant odours or the accumulation of offensive matter resulting from sewage disposal.

To do this, sanitary plumbing and drainage must be designed to carry discharges away so that they:

  • do not cause nuisance or health risk
  • prevent foul air and gases that are generated in sewers, drains and plumbing systems from entering buildings
  • minimise the risk of blockage
  • minimise noise generated by the flow within the system
  • allow for access and cleaning
  • are durable

Acceptable Solution G13/AS1 applies to above-ground non-pressurised sanitary plumbing (i.e. pipes, fixtures and fittings above ground). Acceptable Solution G13/AS2 applies to drainage (i.e. below ground pipework).

Sanitary plumbing and drainage falls under the key plumbing standard AS/NZS 3500 Plumbing and Drainage.

MBIE cited the 2021 edition of AS/NZS 3500 Part 2 as an Acceptable Solution (G13/AS3) in November 2023 with a 12-month transition period ending in November 2024.


Updated: 20 January 2024