Katherine's town water remains safe to drink despite a "spike" in chemical contamination levels.
NT Government officials said four testing results from the town’s water supply have shown results over the maximum allowable 0.07 limit.
Chief health officer Dr Hugh Heggie said there would be “no drastic change” to warnings for Katherine.
“The recommendation from federal authorities and from ourselves is that the water is safe to drink,” he said.
“The levels have risen and we have promised to be transparent with the results,” Dr Heggie said.
Power and Water Corporation now regularly tests Katherine’s water and average results have been tracking about 0.05 to 0.04 PFAS micograms per litre.
Dr Heggie said the average results had most recently fallen back below the 0.07 limit.
He said the federally-adopted 0.07 for the PFAS family of chemicals was a whole of life exposure and not one daily result and the numbers had a 30-fold safety margin.
The PFAS chemicals were contained in firefighting foams used at the Tindal RAAF Base between 1998 and 2004.
The Department of Defence has launched a study into the extent of contamination from the base which has since been found in Katherine’s drinking water.
Primarily the highest results come from bores which are used to shandy Katherine River water during the dry season when flows are low to provide Katherine’s drinking water.
A spokesman for Power and Water said efforts were being made at the town’s water treatment plant keep the contamination levels below 0.07.
The contaminated bores are more heavily relied on later in the dry season.
Dr Heggie was not able to tell Katherine Times the actual numbers of the four high results but said they were “slightly over” the 0.07 limit.
While federal health authorities have placed a 0.07 recommended limit on water contamination, the authorities still say there is no conclusive evidence that PFAS contamination caused health problems in humans.
Authorities recommend people minimise their exposure to chemicals at the levels found by Power and Water as a precaution.
Officials have also asked Katherine residents to consider how much treated water they use on their gardens.