Water main flushing is a necessary program for water agencies to ensure high-quality water. The traditional method of flushing involves opening up fire hydrants and letting the water flow out to scour and remove the buildup in pipes that may cause discoloration or degrade water quality. As water flows at high velocities through the mains, deposits and fine sediment are dislodged. The resulting discolored water leaves the distribution system through the open fire hydrants, runs down the street, and out to the sewer or storm drain systems. This method requires a lot of water. It also causes alarm and sometimes even resentment when everyone is "Doing Their Part" to save water and conserve due to the multi-year drought and our critically-over-drafted groundwater basin.
This May, Soquel Creek Water District re-initiated its Flushing Program, which was suspended due to the water shortage condition in the Mid-County region, and began using a new machine called the NO-DES which eliminates water waste during the flushing program.
In this month's column, we've asked Christine Mead, our Operations and Maintenance Manager, to share and explain this new innovative technology that will keep our pipes clean and save water:
Question: How does the NO-DES Unit work?
By linking together two fire hydrants with a pump, an oversized fire hose and a filtering system mounted atop a flatbed truck, the water is circulated at optimum velocities in a temporary loop. The water passes through filters that remove the sediment and particulates and is returned to the District's water pipes. Disinfectants can be added to further improve water quality. Inline turbidity meters indicate when desired clarity levels are met.
Question: How much did the NO-DES Unit Cost and how did the District pay for it?
The cost of the NO-DES unit and truck was approximately $380,000. The majority of the purchase was funded by the District's Water Demand Offset Program, a conservation program that requires new development to offset their projected water demand by 200% through funding conservation projects in the District.
Question: How much water is saved?
It takes approximately 6 million gallons to flush the District's distribution system using the traditional method. In addition to saving the 6 million gallons, the NO-DES unit can be used in areas with poor drainage that can't be flushed properly with the traditional method.
Question: Who else is using Waste-Free flushing to clean their water mains?
San Jose Water Company and the Cities of Hillsborough, Pasadena, and Fresno are a few of the water agencies in California that I know of that have purchased a NO-DES system.
Question: What areas in the system is the District currently conducting its Flushing Program?
The District is focusing on flushing the western portion of the distribution system first. Flushing the water mains is a necessary step to prepare for receiving water from the City of Santa Cruz as part of the pilot water transfer project. This portion of the District will receive the greatest percentage of Santa Cruz water. It is important to clean the mains to minimize the potential for the release of metals and other solids when receiving the water from Santa Cruz.
Question: Will customers experience anything noticeable when the water mains are being flushed?
District customers may temporarily experience discolored water during water main flushing. Water users are advised not to be alarmed if the water looks rusty as this discolored water is caused by sediments being stirred up within the water mains. If District customers experience any of these changes or see some cloudiness or rust color in their water, we recommend flushing the pipes of the home. Flushing of a customer's home pipes can be done by opening the front outside hose bib until it runs clear. If the water does not clear the first time, wait a few minutes and run the water again. It is also advised that customers make sure the water is clear before doing laundry or other projects for which discolored water could cause problems. It is important to not run hot water if customers notice it is discolored, as the discolored water can be drawn into the hot water tank.
As always, if you have any questions about this month's topic or anything else related to Soquel Creek Water District, feel free to email Melanie Schumacher at or call 831-475-8501, ext. 153 for more information.