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Wastewater systems

Information on installing and maintaining a domestic septic tank.

Home wastewater systems are used on property that's not connected to our reticulated sewer network. That includes houses in all areas outside Gisborne city, Te Karaka, and Te Puia townships. It also includes houses at Wainui beach, Makaraka and rural and coastal areas.

Domestic wastewater systems

There's 2 main types of onsite wastewater systems:

  • one or more septic tanks with a gravity or pumped effluent disposal bed
  • a home treatment system that usually has dripper line disposal.

Your wastewater system may include:

  • sanitary plumbing fixtures connected to drain pipes that take sewage and
  • sullage – that’s the liquid from kitchens, wash basins, toilets and laundries – to the septic tank
  • treatment tanks – passive, aerated or filtered
  • a distribution system, pump, siphon, or gravity fed
  • an effluent disposal system, trenches, beds, mounds, or dripper lines.

How the system works

The type of system you install will depend on your property. Most systems work in a similar way - wastewater is gradually separated, treated, and dispersed, with the help of an army of natural organisms.

Installing a wastewater system

If you’re installing a new system, it’s important that the tanks and effluent beds are the right size so they have the time and area to work efficiently.
Talk to a professional about the best type of system, size and location for your property.

See our list of approved people - they do site assessments and design for onsite wastewater systems  - approved assessors, tank cleaning specialists and service agents 

Installing a septic tank or effluent disposal system will require site evaluation and design before a building consent can be issued.
You'll need to provide details of this work, a site plan and details of the system type, size and layout with your building consent application. 
We will only accept the work of recognised wastewater engineers and those on our list of approved assessors.

Legalisation and consents

Onsite wastewater systems must meet the environmental standards in the Resource Management Act and the Gisborne Regional Discharges Plan.
They must also meet the functional and durability requirements of the New Zealand Building Code and the Building Act.
To install a new system or replace a failed system you will need a site assessment and building consent. The site assessment is to be carried out by an approved assessor, who will design a system or identify the work required to rectify the failure. Or you can use a recognised wastewater engineer to design a system. The design must be based on the site assessment.

Exempt work

Some like-for-like building maintenance projects don’t need a building consent under exemptions in Schedule 1 of the Building Act.  Replacing a failed effluent line is likely to still need a building consent. A failed system won’t comply with the regional rules under the Discharges Plan so the like-for-like option does not apply.

Costs and maintenance

It can cost between $15,000 for a small basic septic tank system to around $22,000 or more for a more complex system (2014 prices).  Transport costs to remote sites could add significantly to the cost.

Systems that have been installed since 2002 may have a filter on the outlet from the second tank or chamber. They must be cleaned regularly or the filter will clog and cause backups in the tank.

Systems with a pump, aerated home treatment plants (AWTS) and low pressure dosed effluent systems have ongoing power costs. An AWTS needs bi-annual maintenance.

All maintenance is at the homeowner’s cost.  See list of specialists and service agents

More information

Information on domestic wastewater systems  - Septic Systems
A guide for owners and users