Rainwater tanks provide storage for non-drinking water use and help create a more sustainable water supply. Rain tanks have two functions;
they reduce the total volume of stormwater which runs off your site, and;
reduce the demand for potable water from the Council water supply system.
Rural properties are required to have a rainwater tank with a minimum size of 22,000 L or equivalent of at least 48 hours storage, whichever is greater.
New urban premises in the Waikato District are not required to have a rainwater tank under the Water Supply Bylaw.
Maintaining tank water quality
Poorly-maintained tanks and roof catchment systems increase the risk to public health as they can significantly lower water quality.
Preventative measures and corrective actions for safe rainwater harvesting include:
Tanks and building consents
A rain tank will require a building consent if:
- the tank will supply roof water to the house
- the Council mains will be plumbed to the tank (eg, backup supply)
- the tank exceeds 35,000L
- the tank exceeds 2,000L and is more than two metres above ground or
- the tank exceeds 500L and is more than four metres above ground.
Unless the tank exceeds the size limits above, installing a rain tank for garden irrigation does not require a building consent.
These criteria apply to both new premises and when retrofitting a tank to an existing property. If a consent is required, it can be included as part of the overall building consent.
Find out more about building consents.
Stormwater attenuation tanks
If you need one of these, it is possible to combine the rainwater tank and stormwater attenuation tank, but the volume of the tank needed should be the sum of the two levels for each function being handled by the combined tank. The top part of the tank drains quickly to buffer storm flows and the bottom saves water for recycling.