Water supply grading
Quality standards for drinking water are set by the Ministry of Health (MoH), through the Drinking Water Standards for New Zealand. Each year the Ministry publishes a grading for every public water supply. Gradings are based on the drinking water standards and indicate how safe each water supply is from contamination.
The MoH grading system has two parts:
- A grading for the source of water and the treatment plant ("A1" to "E"). This relates to the measures taken to limit contamination of the water source and to remove any contamination that is present, by treatment. It is a rating of how safe the water is after treatment, but before it enters the distribution system.
- A grading for the distribution system ("a1" to "e"). This is based on the risk of water becoming contaminated within the local supply pipes, and the procedures in place to minimise the risk of unsafe water to consumers.
The grading range from completely satisfactory ("A1" or "a1") to completely unsatisfactory ("E" or "e") .
Our source and treatment plant gradings are:
- A1 - Te Marua
- A1 - Wainuiomata
- B - Waterloo
- A1 - Gear Island
Our bulk distribution system gradings are:
- a1 - Wellington Region Upper Hutt Porirua
- a1 - Wellington Bulk Lower Hutt
- a1 - Wellington Bulk South Wellington
Lower Hutt, Porirua, Upper Hutt and Wellington city councils are responsible for the grading of their respective reticulation systems (local supply pipes).
Our goal is to have at least an "A1'' grade for the water leaving each of our treatment plants, where that is consistent with the requirements of our customers.
A water supply can't be graded higher than "B" if chlorine disinfectant isn't used in the distribution system. Waterloo has a "B" grading for that reason. Because our aquifer water source is assessed as being free from microbiological contamination, Hutt City Council prefers to receive unchlorinated aquifer water and manage the slightly increased risk of contamination occurring within its distribution system.
Each year the Ministry publishes the Register of Community Drinking-Water Supplies, which lists the water supply grading for every community in New Zealand. To check the grading for your area, click on MoH water supply grading.