Hamilton will require a new water treatment plant costing more than $100 million by 2045, although it could be sooner if the city does not manage its water use better.

Hamilton has been at water alert level two since December due to the increase in water use from residents, but city waters manager Maire Porter said that the restrictions allow the current water treatment station off Peacockes Road the ability to meet the city's growing demand for water.

"As Hamilton is growing, more and more pressure is going on our water assets. We need to ensure we don't over-invest in water treatment infrastructure for the few months of the year when there is particularly high demand," Ms Porter said.

The council has focused on improving the reliability and supply of water around the city with the new reservoir in Rototuna, with another one planned for the Ruakura area.


"The council's Long-Term Infrastructure Strategy identifies that a new water treatment plant costing in excess of $100 million will be needed from 2045, and could be required sooner if we don't continue to manage our demand for water responsibly."

The cost to the ratepayer currently to supply the city with water is expected to be around $28 million in 2017/18.

The city has had an increase in water use since November with an extra 10 million litres being used compared to an average winter's day.

"The city's average use over the past 10 days is 66.8 million litres a day. The highest day of water use so far this summer was on December 6 when the city used 79.2 million litres. In contrast, on an average day in winter the city uses around 50 million litres of water a day."

A million litres is about the same a 6250 bathtubs of water.

Despite the extra use of water, the council is happy at how the public has responded to alert level two.

Alert level two restrictions means sprinklers can be used only between the hours of 6am and 8am and 6pm and 8pm on alternate days. If your street address is an even number you can use your sprinkler on even dates of the month and odd street address number on odd dates of the month.

"We are pleased and want to thank people for how they have responded to alert level two since it came in on December 7, and that behaviour combined with mixed weather has allowed us to remain at this alert level."

"A step up to level 3 is possible, depending on the weather and water use, but is not on the cards at this time."

The council has also said that despite the raised restrictions, they are still within their quota for water taken from the Waikato River.

"Under our water resource consent with Waikato Regional Council there is a maximum amount of water which can be taken from the Waikato River. The amount of water we draw from the river under our consent varies daily depending on demand, and is significantly lower in winter."

Meanwhile, a civil construction company has been convicted of taking water illegally from a council hydrant in October. Evergreen Landcare Ltd was fined $1800 plus costs. The council's compliance manager Trent Fowles says it reflects how seriously the council takes security of the city's water supply.

"Businesses and individuals illegally taking water from Hamilton City Council's network creates potential serious risks for the city's drinking water, as well as creating risks for fire-fighting if the hydrant or pipe is damaged," Mr Fowles said.

Evergreen Landcare had been warned before about illegally taking water. The company previously held permits allowing it to use the approved water take points, but was again observed drawing water from a hydrant in October.

Mr Fowles said he was satisfied with the prosecution.

"We encourage anyone who sees non-council vehicles being filled from hydrants to let us know on 07 838 6699."