The Washington Suburban Sanitary Commission says it is seeing an increase in customers reporting brown or discolored tap water.
However, WSSC officials say based on water tests, they do not believe there is a public health risk.
When you turn on the faucet, you expect the water that comes out to be nice and clear. But thousands of customers in Maryland are seeing something much different.
"I was trying to water the plants … and I noticed the water was kind of like a brownish color," said Gaithersburg resident Melissa Kao. "When we use the toilet, the water is dark too."
Dark and discolored tap water is showing up in homes across Montgomery and Prince George's County. Residents have been sending images to FOX 5 and posting about it on social media.
Apartment complexes have also been notifying occupants.
WSSC have provided a map of the locations where it is being reported.
The utility says it has been receiving complaints since January and the number of calls is increasing. There have been more than a thousand calls in March alone.
"What exactly it is, we don't know," said WSSC spokesperson Jim Neustadt. "There are some indications it could have to do with the harsh winter weather. We're looking at some other possibilities as well."
He said rust and sediment kicked up after water main breaks could be to blame.
Another possible cause is the chemicals that come off of the road after deicing during the winter.
Neustadt said they run half a million water quality tests a year -- numerous times a day -- and results are coming back okay.
"The water has all tested fine," he said. "We meet all of our regulatory requirements."
"People with compromised immune systems and infants probably should think about bottled water, but it's basically safe for most of the people."
If your water is discolored, WSSC wants to hear from you.
"The best thing to do is call us and we can send somebody out and flush the hydrants," said Neustadt. "Even after you flush the hydrants, then there is still going to be water in your home pipes and you will have to go and flush that."
WSSC does not recommend using discolored water to do laundry. If you have to wash clothing, they say to add a product like Rit, a color remover treatment that can be found in most drug stores.
To report a problem, you can call WSSC at 301-206-4001.