Taupō residents are being urged to minimise their water use for the next three to five days following a water main and wastewater pipe break on Lake Terrace yesterday afternoon.
The water main broke yesterday just after 2pm, causing a large washout on the lakefront.
About an hour later the footpath collapsed and took out a wastewater pipe, resulting in about 800,000 litres of wastewater entering the lake.
Chief executive Gareth Green said pumps had been operating through the night to manage wastewater flows at the site of the break and the staff and contractors had been successful in stopping any flow into the lake.
More pumps have been brought in today and sandbags have been put in the manhole and the pipe, as a further preventative measure.
Drinking water was not affected, Green said.
Water sampling will be taken twice daily for at least the next three days to determine E. coli levels in the lake.
"The three biggest risks at the moment are if the sandbags move, if the pumps can't handle the amount of wastewater coming through the system, or if there is heavy rain," Green said.
Water used for showering, bathing, doing laundry and dishes all contributed to wastewater flows and peak times were between 8.30am and 10.30am, and 8pm and 9pm.
"We have a back-up plan to assist with ensuring no wastewater leaks from the pipe, we are asking people to help with reducing the amount of wastewater in the system.
"Another pump is being brought in today to help should we get heavy rain in the next few days," he said.
About two-thirds of the Taupō township contributed to the wastewater flow to the broken pipe.
While Acacia Bay and Nukuhau were not affected in terms of wastewater, Nukuhau residents were still being urged to limit their water use while repairs were made to the water connection.
The supply to Nukuhau was restored yesterday afternoon with a temporary repair but Green said there were likely to be some pressure fluctuations until a more permanent repair was made as there was limited flow.
"There is a valve arriving today that will be installed and the Nukuhau pump station will be recommissioned which should solve many of the low-pressure issues."
Investigations into the cause of the breaks were continuing.
"Our records show that the water pipe was installed in 1999 and it had a life expectancy of 100 years.
"The wastewater pipe was installed in 1973 and had a life of 80 years. This was not related to ageing infrastructure," he said.
"No amount of money could have prevented this from happening."
Green said it was possible the water pipe had split due to ground movement.