Tararua District Council has extended the precautionary boil water notice for Dannevirke until Monday morning.
A council spokesperson said this was due to a forecast for bad weather to continue through the weekend.
It is a requirement by Drinking Water Standards NZ that the council needed to have three consecutive clear water tests once turbidity levels had reduced.
The council was still treating the water supply as of late Thursday for any trace of a bacterial contamination, such as E. coli and test results were negative.
A communications officer said that normally when turbidity occurred, the council would stop taking water from the river and take it solely from the impounded supply.
However, that was not possible because the impounded supply was under repair, so a precautionary notice was issued instead.
Residents were advised to boil any drinking water, as well as water used in food preparation, brushing teeth, making ice and preparing infant or toddler formula.
The notice was issued late on Wednesday after water was found to be turbid.
Communication went out via social media, council website and media, but it was felt as it was a precautionary notice rather than a mandatory one that an extensive letterbox drop was not required.
However, a post on Facebook attracted a number of comments from people saying they didn't get the initial message immediately.
Amanda Lloyd of Sugar and Salt cafe said she had been called at 8am on Thursday and advised of the problem.
She said she had also seen the notice on Facebook.
"I don't know what more [the council] could do.
"We get bad weather and things happen."
However, Rebecca Smith at The Forge restaurant said she had not heard anything from council and only knew about it because she'd seen it on social media.
She said she had rung her grandmother to let her know.
While it was not a big deal for Smith, her concern was for older people who might not have access to the internet.
Council said it had informed local businesses and advised rest homes, pensioners in council housing as well as medical centres, schools and early childcare centres.
The officer said that council would review its communication in light of the community feedback.