Bill Wood has switched to bottled water as he deals with a fine, flaky residue clogging his faucet.

For the second time in a month on Thursday, the north Bismarck homeowner cleaned out the faucet's filter. He's wary of the "chemical debris," as he calls it, and wonders if his water is safe to use.

"My two grandkids that come over to my house every other week, I'm concerned about their welfare," Wood said. "Is it safe for them to take a shower or a bath? I don't know." 

The city is working with homeowners and plumbers to solve a water problem that has presented differently in homeowners' water systems as forms of calcium, some restricting flow. Bismarck's director of utility operations, Michelle Klose, described the problem as a "solids precipitation" from a water chemical reaction confirmed in at least 64 homes out of the more than 19,000 in town. 

She and Greg Wavra, administrator of the North Dakota Drinking Water Program, said the residue is not harmful to people's health. 

A number of linked factors appear to be present in the problem, which seems to be most prevalent in newer homes on the outskirts of town, Klose said. 

Bismarck's drinking water comes from the Missouri River and appears to react, when heated, with magnesium, according to Klose. Magnesium is present in a rod in some water heaters.

Klose said other factors appear to be homes with recirculating pumps – which help provide hot water as soon as the tap is turned on – and cross-linked polyethylene, or PEX, lines, which are plastic-lined water pipes apparently prone to flaking residue. Pipes made of different metals that touch also have presented a calcium buildup restricting flow, she said. Only hot water is affected. 

Wavra said Bismarck's drinking water meets requirements of the federal Safe Drinking Water Act. And calcium buildup, he noted, "isn't anything new" in water systems. 

"When you look at a water tap and you see that white, scaly stuff sometimes, that's what that is, it's just that precipitate coming out of solution around those fixtures," Wavra said.

But after complaints from affected homeowners, the city sent out a May 7 letter and held a June 4 informational meeting to share findings on how to mitigate the problem, such as using aluminum rods in water heaters and lowering the heat.

The letter said the city's new water intake in 2014 and its switch in 2013 from chlorines to chloramines, which are water-disinfecting agents, are unrelated to homeowners' issues.

"We have discussed this question of chloramines specifically with the (state) Department of Environmental Quality and we both agree that the use of chloramines is not a contributing factor to the solids precip affecting PEX lines with recirculation pumps," Klose said. 

The issue essentially stemming from materials in newer homes' water systems reacting with the city's drinking water has been known for a few years, according to Klose.

"But when you're dealing with this small a number of complaints when you're looking at almost 20,000 homes, it's really hard to pinpoint these types of issues," she said. "But some homes are having significant issues, and some homes are having very minor issues." 

Ken Hoff said his family first noticed decreased water pressure about a year after building their home in north Bismarck in 2014. They consulted a plumber, who pointed out the sandlike residue in their lines. Hoff said another plumber linked his problem to the chloramine in city water forming a sand or pebble when heated.

He spent $2,500 last year for labor in replacing his water heater, installing an inline filter and flushing out his PEX lines twice. The water pressure is a lesser issue now, he said. Once a month he drains the filter. He changes it after six months.

Hoff said he's not upset and credits the city for trying to solve the problem. 

Wood said he doesn't plan on replacing his plumbing, but he would like to know about the safety of his water. He first noticed the water issues when he moved into his house in December.

He points to hot water as a component, but he doesn't have magnesium in his water heater. He's also talked with neighbors who have similar problems. 

"We're trying to pull the right resources together with the homeowners to see if we can try and help them find some solutions," Klose said. 

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Reach Jack Dura at 701-250-8225 or jack.dura@bismarcktribune.com.