Council Encourages Private Well Testing

The Waimakariri District Council has released an information booklet for owners, or prospective owners of a private well. The booklet provides guidance on how to drill a new well, test water regularly, and what to look for when buying a property with a private well.

Maps of well testing results give an indication of where there are particular contaminants in the District to watch out for.

The booklet release is timed with a report on the second year of a Council-led study of 19 private wells in the Cust and Eyreton areas.  Nitrate and other chemical parameters were analysed in private wells, in response to a recommendation from the Waimakariri Water Zone Committee. Cust and Eyreton have been selected for annual sampling because of reports of elevated nitrate levels.

The study results highlight the importance of private well owners to understand that they are responsible to undertake their own water monitoring, and what frequency to test their water.

The study found one of 19 private wells with nitrate above the Maximum Acceptable Value (MAV) of 11.3 milligrams per litre (mg/l) nitrate-nitrogen (equivalent to 50mg/L nitrate), as set out in the Drinking-water Standards for New Zealand.

Consumption of nitrate over 11.3 mg/L (equivalent to 50mg/L nitrate) can cause adverse health effects for unborn babies, young infants, and those with rare metabolic disorders. Therefore it is important to test regularly, at least annually, to check that water is safe to drink. Nitrate levels can change seasonally.

“The test for nitrate is particularly important in the inland plains areas of our District, stretching roughly westwards of Rangiora towards the hills” says Council’s Water Environment Advisor Sophie Allen. “Nitrate is just one contaminant that all well owners should look for, with testing also recommended for other potential contaminants such as arsenic, and bacteria such as E.coli”.

Elevated levels of nitrate over the MAV had been found in an Environment Canterbury monitoring well in the Cust area, and in private wells in Eyreton previous to the Council study.

Utilities and Roading Manager Gerard Cleary says “Private well owners should have their water checked by an accredited laboratory to ensure water is safe to drink.”

Affordable treatment options exist for nitrate removal. However, many standard filters are not adequate for the removal of nitrate, and advice should be sought from a water treatment specialist on the appropriate filtration system for removal.

Gerard advises “There is no need for landowners supplied by a Council reticulated water scheme to test their water. The Council supplies have regular testing, with no water supply in the District affected by high levels of nitrate or other contaminants.”

Recommended Testing Regime:

WDC recommend a full chemical test (for a wide range of contaminants) when you purchase a property or drill a new well as initial screening. Follow-up testing is prudent every 6-12 months after the initial test.

Find out more:

The Waimakariri District Council booklet ‘Managing a Private Water Supply Well’ can be found here:

For health information about nitrate visit