UPDATED 3.49PM Water has been added to Lower Hutt's water supply after a reservoir in the area tested positive for E coli.

The Hutt City Council says it started chlorinating the water supply for 76,000 Lower Hutt residents on Saturday after a routine test from the Naenae reserve came back positive for E coli.

The council said while E coli was an indicator, it had not yet been confirmed whether the water was actually contaminated, and Wellington Water staff were adding the chlorine in as a precaution.

The results of whether the water is contaminated will be available on Sunday night.

The council said water from taps was safe to drink and did not need to be boiled, although residents may notice a slight taste.

Routine tests often came back positive for E coli, and chlorine was always added until it could be confirmed there was no risk, it said.

Although the council is insisting the water is safe to drink, resident Jo Hall isn't taking chances.

"I am steering clear of it, I'll buy bottled water- it's also like taking a shower in a swimming pool" she said. 

The public wells at Buick Street in Petone, and Dowse Square in Lower Hutt remain unchlorinated.

Water in Wainuiomata, Stokes Valley and Manor Park is already chlorinated.

The test comes just days after Napier's water tested positive for E coli. It's also added chlorine to the water as a precaution.