The Rangitikei District Council has been using activated carbon to address odour and taste issues with its water supply.
Last week the water went discoloured and odorous with some residents describing the water as coffee-coloured and undrinkable.
Chief executive Ross McNeil said samples had been sent away to a lab and given the all clear.
"We've done the testing and they're 100 per cent happy that there aren't any nasty algal spores there," he said.
He said council staff had put it down to heavy rain and warmer weather which had stirred up the damns the water was taken from.
Marton's town supply was a surface water take which was chlorinated, Mr McNeil said.
"We've had an extended period of rain," he said.
"Really it's a process of allowing the lake to settle down."
Mr McNeil said council would continue to be monitor the water and had been using activated carbon to help improve taste and odour .
"My understanding is it's not necessarily 100 per cent fixed but it's the best tool we have available to address taste and odour issues.
He acknowledged there had been complaints and said council would investigate why it was happening.
"Once the guys have got on top of this, we'll have a sense of what the actual causes are and if there's something more than heavy rain.
"It might be one of those things that we can't actually put a finger on."