Hydrant Flushing

Hydrant Flushing2017-18 Program is Complete

Details for 2018-19 Program Coming Soon

The City of Napa Water Division conducts a Hydrant Flushing Program each winter to maintain water quality throughout the system.

City staff isolate flushing areas by closing pre-selected system valves. This state of the art program directs the water to flow in one direction ("unidirectional") and increase the velocity of the water in the pipes, thus more effectively removing particles and minerals from the pipe compared to just operating hydrants without closing valves. Although customers continue to have water service during this program, flushing operations may activate low-pressure alarms on automatic fire sprinkler systems due to temporary reductions in water pressure in the vicinity of flushing operations.

Current Flushing Area


Next Flushing Area


Hydrant flushing is a periodic maintenance activity to clean and flush the City water mains. Fire hydrants are opened to move a large volume of water at a higher than normal velocity through the mains. This procedure mobilizes particles and minerals that have settled over time and flushes them out of the system. This activity assists the City in maintaining the highest quality of water in the public water system.

The flushing program may cause periods of discolored water and reduced water pressure in localized areas where flushing is being conducted. The discoloration is due to mobilization of particles and minerals by the high velocity water before they are discharged through the fire hydrants. The water will remain safe to use and generally clears within a few hours after flushing has been completed. Residents should monitor their water prior to starting laundry, especially when washing white clothes.

Commercial customers, especially businesses that serve the public, should be aware of the water quality while flushing is taking place in their area. Due to the nature of the program, it is difficult to determine the exact day an area will be flushed; however, on average, each flushing set takes 1 to 3 days to complete, depending on the quantity of water mains to be flushed and the number of valves that are operated.

The City thanks Napa residents and businesses for their patience and apologizes for any inconvenience our program may cause. Please contact the City of Napa Water Division at (707) 257-9521 with any questions or concerns, or consult our Frequently Asked Questions (FAQs) below.