Woodstock Fire Department officials Monday began annual fire hydrant maintenance and said it will last through June 12.

Fire officials said residents may notice some temporary discoloration in the water, which can stain light-colored clothing. They said that it’s not harmful to drink or use. The discoloration results from water-line sediment stirred up during the testing process.

Officials said the testing involves fire department employees flowing hydrants until they’re clear. Smaller lines leading to individual homes may then still have cloudy water, which can be remedied by running it until it has cleared up.