Our potable water
The availability of clean, safe to drink, water is fundamental to the health and welfare of the Selwyn Community. There are nine river/gallery intakes, and 24 deeper groundwater takes. Drinking water is provided by the Council to over 75% of the population of the District. Water is supplied for public needs including household, gardens, and public reserves.
How we comply
All our Water Supply schemes are monitored and tested on a regular basis for the presence of bacteria.
- Our Water Quality monitoring is governed in compliance with Drinking-water Standards for New Zealand 2005.
- All our Water Supply schemes have a Water Safety Plan (WSP) currently approved by the CDHB (copies of our WSPs are available on request).
- Our Water Supply Bylaw 2008 applies to water supplies under the care, control and management of, or water provided by, the Selwyn District Council and other water related bylaws.
- More about Water sources and ways of treatment
How you can help
Disinfect your water storage tank
- If you have own potable water Storage tanks in your property, it needs to be disinfected and maintained on a regular basis. View guidelines and instructions on how to Disinfect Water Storage Tanks [PDF, 33 KB]
Get your backflow protection tested
- To minimise the risk of contamination to the water supply, an appropriate level of backflow prevention is to be provided on all connections to water supplies. All privately managed backflow devices must be included in the property’s compliance schedule and be maintained fully functional.
- Backflow prevention device installed at high, and medium hazard properties must be tested annually by an Approved Backflow Technician or Independently Qualified Person (IQP) at the property owners expense.
- The backflow prevention policy sets out the backflow prevention requirements for new and existing properties in the district.
Flush your taps
- Traces of metals – in particular lead – are of concern because over time they pose a potential health risk, especially if consumed from childhood. The whole phenomenon is technically known as ‘Plumbosolvency’.
- The Ministry of Health therefore recommends that people do not drink the first mugful of water if their tap has not been used for several hours overnight, or after long absence from your property. Instead, people should run the tap for a second or so, which will quickly flush-away any water that has become contaminated with lead or any other metals from the plumbing fittings.
- Additional details on this issue can be sourced from the Ministry of Health website – www.moh.govt.nz or the Plumbosolvency Q & A Sheet [PDF, 34 KB]
Our water quality tests results
- Over 400 samples are taken on a weekly basis and sent to the lab for testing.
- There are 9 river/gallery intakes and 20 deeper groundwater takes. Source, treatment plant and reticulation water is regularly tested for the presence of bacteria.
The water is tested for the following parameters on a regular basis:
GUIDELINE VALUES (*)
Ecoli (post treatment)
(**) – Mean Probable Number
The results for E-coli normally take a 24 hour turnaround time. Every two years the water is also tested for the parameters as noted below:
MAV & GUIDELINE VALUES (*)
Total Arsenic (g/m³)
Total Chromium (g/m³)
Total Lead (g/m³)
Total Nickel (g/m³)
pH (pH units)
7.0 - 8.5
Total Alkalinity (g/m³ as CaCO₃)
Free Carbon Dioxide (g/m³ at 25°C)
Total Hardness (g/m³ as CaCO₃)
Electrical Conductivity (mS/m)
Electrical Conductivity (µS/cm)
Approx Total Dissolved Salts (g/m³)
Total Boron (g/m³)
Total Calcium (g/m³)
Total Copper (g/m³)
Total Iron (g/m³)
Total Magnesium (g/m³)
Total Manganese (g/m³)
Total Potassium (g/m³)
Total Sodium (g/m³)
Total Zinc (g/m³)
(*) Guideline Values are in accordance with Drinking Water Standards NZ.
These results are a reflection that the water supply communities generally have access to high quality water.
Turbidity is also sampled for the water schemes.
Water Treatment / Barriers
Ultra Violet Light
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