Heavy rain forecast for Taupō today is expected to hamper recovery efforts following the major wastewater spill to Lake Taupō on Tuesday, and could increase the risk of more wastewater entering the lake.

The Metservice is warning the district to expect between 60 to 80mm of rain to accumulate between 9am and 4pm today with peak intensities of 25 to 35mm/hr.

The water main broke on Tuesday just after 2pm causing a large washout on the lakefront. About an hour later the footpath collapsed, damaging a wastewater pipe causing around 800,000 litres of wastewater to enter the lake.

Lake Taupo Mayor interview discussing the wastewater spill entering the Waikato River. Video / Focus Live

Yesterday the Taupō community was warned it could take three to five days until wastewater flows could return to normal. However today after updates the repair timeframe, a week was now looking more realistic, chief executive Gareth Green said.

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Around two-thirds of the town is affected and residents are being asked to minimise water use as much as possible to avoid overloading the temporary wastewater repair.

Today, the forecast rain is the biggest concern. While some of the largest pumps in the country had been brought in to help manage wastewater flows at the site of the break to reduce the likelihood of any more entering the lake, the site is now at pumping capacity, Mr Green said.

"With the forecast heavy rain, it is even more critical that our community tries to minimise water use as much as possible. It is probably more important today given the weather is something that is completely out of our control."

Rain typically increases flows in the wastewater system as it can enter through a number of ways, including gully traps and leaks around manholes.

The site of the water main break and wastewater spill on the Taupo lakefront on Tuesday.
The site of the water main break and wastewater spill on the Taupo lakefront on Tuesday.

About two thirds of the Taupō township contributed to the wastewater flow to the broken pipe. Peak wastewater flows occur between 6am and 9am and 3pm and 9pm.

While Acacia Bay and Nukuhau are not affected in terms of wastewater, Nukuhau residents are still being urged to limit their water use while permanent repairs are made to the water connection.

Between 70 and 80 per cent of Taupo's wastewater poured into Lake Taupo. Photo / Helicopter Services
Between 70 and 80 per cent of Taupo's wastewater poured into Lake Taupo. Photo / Helicopter Services

Health warning signage has been installed at the site of the break and along the route of the plume, including along the Waikato River. They will remain in place until water sampling shows E.coli results are within recreational health guidelines. Water sampling is being undertaken twice a day.

Drinking water across the district is not affected. Investigations into the cause of the breaks are continuing.

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Regular updates are on the council's website taupo.govt.nz and Facebook page.