Hastings people have been reassured there is no physical connection between Havelock North and Hastings water.
Hastings District Council water services manager Brett Chapman told a press conference this morning that Hastings water was sourced from more than 60m deep with five confining barriers.
Earlier the council said an e-coli indicator has been found in one of nine water tankers used to supply drinking water to Havelock North residents.
The council made the decision to chlorinate the water supply and emailed the DHB to tell them about it. The DHB confirmed chlorination today was appropriate, Mr Chapman said.
The suspect water tanker had a sign placed on it as soon as the positive indicator test was received and the tanker was later removed.
It had been at Havelock North High School car park since Monday.
Residents were directed to the tankers by the Hawke's Bay District Health Board after thousands became ill from campylobacter in the water last week.
Those who took water from the site and still have it in containers were asked to dump it.
All tankers were made vandal-proof.
The tanker had been filled up in Hastings. Hastings mayor Lawrence Yule said the decision had been made to chlorinate the Hastings water supply immediately as a precaution, despite the majority of indicator tests returning negative.
The water from the other tankers had been tested and was clear, however the water in all the tankers was now chlorinated.
It is believed that the cause was likely to be the tanker, however as a "super precautionary approach" the water supplies for Hastings and Flaxmere were now being chlorinated.
The daily tests for those supplies have been clear.
Mr Yule said, as a precautionary approach, people may want to boil any drinking water or use bottled water while the chlorine works its way through the system.
He said the test was an indicator, but the council had decided to make the information public.
"We will know the full results tomorrow. Seventy per cent of these test come back negative, but we have decided as a precaution to chlorinate the Hastings water supply."