The Defence Department last week confirmed it “was considering supplying eligible households with rainwater tanks” although Katherine Times has been told by several residents the offer had already been made.

“They see it as a cheaper option than bringing bottled water to us every week,” one resident, who did not want to be named, said.

“This way it is one expense and it’s over … they’ve offered to fill it with clean water too.”

It is now believed between 20 and 30 families neighbouring the base are receiving “alternative sources of drinking water” after chemicals called PFAS were found in ground and surface water testing.

Traces of PFAS have also been found in Katherine’s drinking water although at levels well below allowable limits.

With a further year of testing to come, initial tests found PFAS used in firefighting foams at the base between 1988 and 2004 have leached from the base into the groundwater.

“Defence has adopted a precautionary approach and is providing alternative sources of drinking water to eligible residents located in close proximity to the base who do not have a town water connection, and rely on the use of a bore for drinking water,” a spokesman said.

“Defence will also provide water to residents if drinking water is sourced from a rainwater tank that contains, or has contained, bore water in the past.”

Many questions were asked at the defence department sponmsored water forums in Katherine late last month on the use of rainwater tanks.

Many residents said bore water was regularly used to top up supplies during the long dry season and defence officials agreed it may mean the tanks themselves are now contaminated.

“Defence may also provide drinking water to residents in other exceptional circumstances,” the spokesman said.

“Each household’s drinking water requirements will be assessed on a case-by-case basis,” the spokesman said.