Ballarat Health Services has closed a hydrotherapy pool after tests for legionella returned a suspected positive reading.
It will take another week to confirm whether the bacteria is present in the water collected from a water pump system at the Queen Elizabeth Centre.
The bacteria can causes flu-like symptoms associated with legionnaires' disease.
The centre's Wendy Hubbard says it will dose the pool with extra chlorine today and may individually contact the 200 people who used the pool in the past week.
"We have this testing done every month and in all the time the pool has been open, we've never had a positive test," she said.
"The pool actually has chlorine levels which are set by a computer and they're tested every day.
"It wouldn't be surprising if at the end of 14 days it isn't legionella that's grown but we're erring on the side of safety.
"We actually are very, very careful because we're part of a hospital and the people who go into our pool are sometimes frail and have disabilities.
"We are very meticulous about our testing regime, if we need to increase our testing then that's what will do but it is much, much more monitored than certainly a home pool because our clients are much more vulnerable."