Brown water pours from an opened hydrant on Wednesday in Potomac, Md. Montgomery County residents have been making reports about it since March. Officials blame salt and manganese. (Michael S. Williamson/The Washington Post)

If you live in Montgomery County and are wondering why your drinking water has taken on a brownish tinge, blame the winter weather.

The water utility for suburban Maryland said the salt used to treat Washington-area roads and sidewalks during the icy winter probably caused significantly higher levels of sodium chloride in the Potomac River, which provides drinking water for the county.

The Washington Suburban Sanitary Commission (WSSC) suspects the levels — the highest seen in its drinking water system in at least a decade — led to increases in a mineral that the utility says is responsible for brown water flowing from some taps in Montgomery.

WSSC has received 3,005 complaints about brown tap water since March, with 420 of those so far in June — three months since the region’s last measurable snowfall.

“We had historic levels of sodium chloride in the system, and now we’re seeing this happening,” WSSC spokesman Jerry Irvine said of the brown water. “Our working theory is there’s a cause and effect.”

Washington Suburban Sanitary Commission inspector Craig Brown checks water clarity against a tan work glove. (Michael S. Williamson/The Washington Post)

But Irvine said the water is safe to drink, and sodium levels have dissipated since the spring. While brown water isn’t “aesthetically appealing,” Irvine said, water quality tests conducted daily throughout the system have shown no problems.

Some environmentalists have long questioned the impact of road salt on drinking water and freshwater animal habitats. However, the brown water also highlights continuing problems with WSSC’s decaying infrastructure. The discolored water is appearing in older areas of Montgomery, particularly Bethesda, Chevy Chase and Rockville. Those areas have cast-iron pipes — up to 60 years old — that have corroded and are particularly susceptible to collecting manganese, the mineral that WSSC said causes the brown color. Manganese sticks to the pipes’ rusted interiors as a dark, powderlike substance, it said.

When the utility diverts water, it disturbs the flow in nearby pipes and causes manganese sediment to get into the water, but it doesn’t seem to stick to newer ductile iron pipes or those lined with concrete, WSSC said. The problem hasn’t been happening as much in Prince George’s County, which WSSC also serves, because its drinking water comes primarily from the Patuxent River, where two reservoirs allow sediment to sink to the bottom before water enters the treatment plant, the utility said.

Officials for D.C. Water and Fairfax Water say they haven’t seen any problems.

However, Jeanne Bailey, a spokeswoman for Fairfax Water, said the utility saw elevated levels of sodium in the Potomac this spring. The levels were higher than the utility had seen “in a number of years,” Bailey said, and Fairfax Water attributed it to road salt. She said the water remained safe to drink, and the utility received no complaints.

Thomas Jacobus, general manager of the Washington Aqueduct, said the facility saw no increase in sodium chloride.

A spokesman for the American Water Works Association said he hadn’t heard of other U.S. utilities dealing with more sodium chloride or manganese-related brown water.

Irvine, of WSSC, said the utility suspects much of its problem stems from the fact that the WSSC intake pipe on the shore of the Potomac is just downstream from where the Watts Branch enters the river. The Watts Branch is fed by tributaries throughout densely developed Rockville and Potomac. The stream, Irvine says, likely has higher concentrations of salt that then runs almost directly into the treatment plant’s intake pipe.

Higher sodium levels can wreak havoc on older pipes, said Sujay Kaushal, a University of Maryland geology professor who studies Washington-area waterways. He said sodium chloride in groundwater leaches manganese from the soil and sends it into streams. Higher-sodium water also is more likely to disturb any manganese sediment on pipe walls and can leach manganese from the iron pipe itself, Kaushal said. Manganese also gets into older pipes via groundwater that seeps through cracks, he said.

Studies have shown road salt has contributed to increasing salinization of streams and rivers that supply drinking water across the country, Kaushal said.

“Road salt is a direct threat to the drinking-water quality in our region and other regions,” Kaushal said. “We’re finding it sticks around for a long time. Even if we stopped using road salt now, our surface waterways would still be salty for decades afterwards.”

WSSC officials said the utility received a few complaints of salty water this spring, but that the plant was able to dilute it during the treatment process. Still, the brown water continues to worry some Montgomery residents.

Tara Bizjak said the faucet for the tub where she bathes her young daughter has spewed brown water about once a week since February. She said she runs the tap until it becomes more clear, but the bathwater remains “slightly discolored.”

“What are we going to do?” said Bizjak, who lives in Rockville. “We can’t not bathe our 2-year-old.”

When she changed the sediment portion of the filter on the kitchen faucet two weeks ago, she said, the outside was an orange-rust color.

“It just looked gross,” said Bizjak, a government employee. “They say it’s safe, but I don’t know. It’s not pleasant to look at, but we don’t know what else to do.”

WSSC responds to complaints by sending out crews to open nearby fire hydrants to flush out the system. The utility also is working on a plan to similarly attend to older parts of the system more regularly, Irvine said. Local highway agencies said they doubt their road salt is to blame because they used less salt this winter than last.

“The Potomac starts in Pennsylvania, and we’re downstream, so we get everything,” said Branco Vlacich, Northern Virginia district maintenance engineer for the Virginia Department of Transportation. “It could be Pennsylvania is using a lot of salt, and that’s ending up in the Potomac.”

Keith Compton, chief of highway services for Montgomery’s transportation department, said the agency counts on salt to prevent and melt ice.

“I’d think WSSC would be prudent to take a more holistic look at that, because we’ve always used salt,” Compton said. “We know for sure that salt saves lives.”

Kaushal, the professor, said the amount of salt spread onto roads doesn’t affect the concentration of it in local waterways as greatly as how much snow melts — and how quickly. Fast-melting snow can send higher concentrations of salt into streams, he said.

Have brown water? WSSC said customers can make reports by calling 301-206-4002.

Angela Fritz contributed to this report.