Would you drink it? Marton man Michael Gough is frustrated his tap water is brown again, and is blaming it for his entire family breaking out in a rash.

A mistake at the water treatment plant is to blame for brown, foul-smelling water pouring from taps in a Rangitīkei town, but officials say it shouldn't be making people sick.

Some Marton townsfolk are complaining on social media about rashes after taking a shower – or a burning sensation in their mouths and peeling lips after trying to choke down a mouldy tasting glass of water.

Brown water's been a problem over the past week, after a miscalculation at the Marton water treatment plant. But the Rangitīkei District Council couldn't find anything in the water that could be causing such severe reactions.

Marton resident Michael Gough said the discoloration and smell had been an off and on problem for decades. He's fed up with it, from clothes coming out of the wash stained to frequent trips to collect bottled water.

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Initially, Gough thought this time was more of the same – even when everyone in his family came down with a rash.

"I thought something in our house was causing it. I didn't think it might be the water, until I saw other complaints of rashes and blistering after showers on social media."

DAVID UNWIN/STUFF Rangitīkei District mayor apologises for the treatment plant error that caused the foul brown water, but says the water is safe to drink.

​Aleesha Rubie​ said even after living in Marton for two years she still couldn't believe how frequent the water problems were.

"I've lived all across the country, and never had water like this. It's quite shocking after having clear tap water all my life."

Rubie had also broken out in a large rash down her back, which stung in the shower.

She suspects the water is inflaming her daughter's eczema. But that could also be a reaction to the more fragrant washing powders she's been using to overpower the water's "swamp smell" on their clothes, she said.

Council chief executive Ross McNeil said the council was aware of people's concerns, but hadn't found anything in the water that could cause rashes or blisters.

He understood complaints had also been made to MidCentral DHB's medical officer of public health, who investigates potential health risks.

Meanwhile, the council will run a battery of additional tests to double check it hadn't missed anything in the water, he said.

GRANT MATTHEW/STUFF Rangitikei District Council staff didn't find any signs the water could cause blistering and rashes, but are doing additional tests to double-check.

McNeil said Marton had struggled with brown water since it was founded. The area's water has high levels of manganese minerals, which causes a brown slime in pipes and waterways.

When the slime comes loose in the water system, the town's water turns brown.

McNeill said the council hired independent experts to develop a more effective treatment regime, following a particularly bad bout of brown water last winter, to remove the mineral before it got into the main water system.

The foul water often follows heavy rain, like Rangitīkei got over the Christmas holidays, which stirs up the manganese slime in the waterways.

The new treatment regime has largely kept the water clear, but a recent misjudgment of the chlorine levels allowed the manganese into the mains, McNeil said.

That has now been corrected. The discoloration is expected to fade as the system is flushed out, and the water should be completely clear again by the weekend.

Rangitīkei mayor Andy Watson has apologised for the blunder in a video on YouTube.