Tuesday December 15, 2015

The City of Napa Water Division has begun the annual Unidirectional Hydrant Flushing Program which will continue through March 2016. Flushing will take place in parts of north Napa, Browns Valley, Alta Heights, the Soscol Gateway, Napa Valley Corporate Park and Silverado Country Club service areas. 

Despite the ongoing drought conditions, the flushing program is necessary. If we do not routinely flush our City water mains, water quality will degrade. When pipes are not flushed, sediment can build up, react with chlorine, and increase the potential formation of disinfection byproducts, as well as require an increased amount of chlorine to ensure that the water remains potable. It is estimated that the flushing program accounts for about one-tenth of one percent (0.1%) of the City’s annual water use.

Unidirectional flushing is completed by opening fire hydrants 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, helping to maintain the highest quality of water in the public water system.

Flushing may cause periods of discolored water and reduced water pressure in localized areas where flushing is being conducted. The discoloration of water is due to mobilization of particles and minerals that have settled in the water main by the high velocity water before being 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.

During the Unidirectional Hydrant Flushing Program, City staff will isolate the flushing areas by closing pre-selected system valves. Although customers will continue to have water service, flushing may activate low-pressure alarms on automatic fire sprinkler systems due to temporary reductions in water pressure in the vicinity of flushing operations.

Dechlorination tablets are used during flushing to remove chlorine in the water before it goes into the storm drain system and eventually into the Napa River. Due to the high volume of water flowing from the hydrants, the dechlorination tablets may cause some bubbling of the water as it runs in the gutter, giving it a soapy appearance. The tablets are environmentally safe and are being used to protect the river.

Due to the nature of the flushing program, it is difficult to determine the exact day for flushing in a given area. For that reason, the Water Division updates a web-based map daily, showing the region being flushed each day and the region that will be flushed next. The maps and other updates can be found at www.cityofnapa.org/water

Contact the City of Napa Water Division at (707) 257 9521 with questions or concerns.