The St. Charles Fire Department is testing hydrant flow in the city Tuesday morning. Residential water may turn a little rusty following the testing.

Here’s what you need to know, according to the city.

Crews will conduct hydrant flow testing at 3342 West Main St. on Nov. 25. The tests begin at 9 a.m. and should be completed within an hour.

“Residents may experience rust in the water during or immediately after the testing procedure,” the city posted. “The water is safe, however, you may want to refrain from doing laundry until the water is clear.”

The city said “rust-removing solution packets” are available to clean up any discolored clothes from being laundered. To obtain one of the packets, contact the Public Works Department at 630-377-4405. The packets work best if you keep the discolored clothing wet, according to the city.

“It is advised that drivers use caution in driving through areas being flushed due to water that may be on the pavement,” the city posted.

Similar rusty water is often the product of city hydrant flushing that usually happens twice per year. The practice of flushing hydrants improves water quality and eliminates rusty water during periods of high water demand.

Murky water is caused by iron and mineral deposits that get stirred up during the hydrant flushing process.

Running cold water often helps eliminate the rusty water.