Water New Zealand says many communities in Aotearoa New Zealand are at serious risk of illness because of poorly installed and maintained onsite wastewater management systems.

Chief executive Gillian Blythe says Queenstown’s cryptosporidiosis outbreak has again highlighted the need for better and more consistent regulation of onsite wastewater management systems.

“Across the country it has been estimated that there are between three and four hundred thousand onsite treatment units. This means that about 18 percent, or nearly one in five New Zealanders, rely on onsite units for their sewage treatment.

“In Queenstown about ten percent of the population rely on onsite wastewater management systems or septic tanks.

“We don’t know that Queenstown’s reticulated drinking water was the source of the faecal matter that caused the illness in the town. But we do know that onsite treatment systems can pose a real risk to the health of drinking water and the wider environment, particularly if they are old and poorly maintained.

“For instance, it would only take one substandard onsite wastewater system at a school, camping ground, marae or single rural dwelling to put a neighbouring community water supply scheme at serious risk.”

She says the sector has been concerned for many years about the lack of national standards and guidance for onsite wastewater.

“In 2008, there was a proposal to develop a national environmental standard requiring many on-site wastewater systems to hold a warrant of fitness ensuring they were properly maintained and functioning.

“Unfortunately that never progressed and onsite wastewater management has continued to remain outside the three waters reforms.

“We need the government to take a more pro-active approach to this important, and largely forgotten, risk to public health.

“The lack of consistency has meant that important safety issues such as separation distances between onsite wastewater and drinking water sources vary across councils and are not always understood by those enforcing them.”

Homeowners with onsite wastewater systems also have an important role to play. Water New Zealand has published an overview and detailed technical guide to help them understand risks and responsibilities https://www.waternz.org.nz/OWMScompleteguide

Experts in onsite wastewater management can also be contacted through the Water New Zealand OWMS special interest group.

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