In the flood-affected town of Rochester, in northern Victoria, residents have been told they cannot flush their toilets for at least the next two weeks after the sewerage system was destroyed by floods.
Coliban Water said it would be at least six to eight weeks until the sewerage system was back to normal.
The town has a population of 3,000, but thousands evacuated last week when floodwater inundated the town.
Only eight homes were spared from damage.
Rochester Business Network president Glenda Nichol said she was shocked to hear the community would be without functioning toilets and showers for weeks.
"People can't move back to their houses,"she said.
"For the business owners, how you can run a hotel if your toilet isn't operational?
"This has a devastating impact on our town. It's such a challenge."
Sewerage network underwater, Coliban Water says
Coliban Water managing director Damian Wells said the majority of the town's pump stations and sewer network was underwater.
Portable toilets and showers have been installed in a park on Queen Street, Rochester and on the corner of Pascoe and Baynes Street, Rochester.
For those dealing with excess sewage waste at home, Mr Wells said the advice was to "flush it into the street if you can, push it into the stormwater network, instead of the sewer network."
"The whole sewer network was inundated by floodwater, and until that flood water recedes, until you can get the pumps moving, nothing will be moving through that network," he said.
Coliban Water is urging residents not to flush their toilets.
Mr Wells warned toilets would start to clog up if people continued to flush.
"We've got some toilet blocks and shower blocks on the east and west side of Rochester to support the short-term recovery," he said.
"We're asking people when you're hosing out, when you're doing your recovery network, try not to put any of that into the sewer network."
Mr Wells said crews had travelled to Rochester to assess the damage, but repairs could take some time.
"The sewer network is not currently functioning," he said.
"We will look for any short-term solution to explore any way of bringing the system online sooner."
He said it was critical people minimise producing wastewater, including from toilets, showers, baths, dishwashers and washing machines.
In a statement, Coliban Water said: "Residents may be able to flush their toilet or have a shower, but this wastewater is entering our system and is unable to be pumped to the plant."
Long way to go with clean-up
Ms Nichol has been busy helping businesses and residents with the clean-up and has called for the government to send resources to help with the recovery effort.
"We've got three schools and a hospital that is ruined," she said.
"The year 12 students are meant to be doing their exams in a week, with no access to schools."
Parts of the town are without internet, while water continues to be pumped out of businesses and streets.
"People who were a long way from Rochester have had water go right across their farm, right through their house, and they had no warning or preparation."
