Keeping Hydrants Flush with Safety
July 1, 2026
Rockville residents might not give much thought to fire hydrants, but the city spends a good deal of time and money ensuring hydrants are in working order, so that if they’re needed, they’re ready.
Rockville maintains approximately 180 miles of water pipes, 4,100 valves and 1,300 fire hydrants. The city is divided into 39 water-main districts that undergo water-main flushing in rotating cycles.
Flushing hours take place from 7 a.m.-3 p.m. Monday-Friday. Some parking restrictions may be needed to allow access to water valves.
Rockville’s systematic flushing program began in June and will run through late October. Department of Public Works crews open and close water valves and fire hydrants in a certain sequence, producing enough water velocity to scour the pipes of sediment.
By operating the water main valves, crews can assess their functionality, leading to better system maintenance and operation, and better water quality for homes and businesses. Low pressure or water discoloration may occur after flushing. Run the cold tap until the water is clear. These conditions are temporary and should clear up within a few hours.
To learn more and find the flushing schedule and a map of districts, visit rockvillemd.gov/services/water-main-flushing.
Why Are Hydrants Painted Different Colors?
The colors indicate the rate of water flow through the hydrant. It is important for firefighters to know the flow so that they can quickly determine which hydrants to connect their hoses to.
Hydrants are painted to follow National Fire Protection Association guidelines. Hydrant barrels are yellow to increase their visibility at night. The tops of the hydrants are painted a color that indicates their flow rate. Hydrants with flows less than 500 gallons per minute are red; up to 999 gpm are orange; up to 1,499 gpm are green; and 1,500 gpm and greater are blue.