NO-DES Truck Becomes Part of the Utility’s Conservation Arsenal
Water is a precious commodity in our arid community, and we’re always looking for new ways to conserve it. The Water Authority’s newest conservation tool is a locally manufactured piece of equipment that will save millions of gallons per year during routine waterline flushing.
The Neutral-Output Discharge Elimination System (NO-DES) is a self-contained, truck-mounted filtration system designed to eliminate the water waste associated with hydrant flushing. Routine flushing, usually done in response to complaints of “dirty” or discolored water, can send hundreds of thousands of gallons down the storm drain with each occurrence. But with NO-DES, the water is cleaned and returned to the system with zero waste.
Why flush the hydrants?
The Water Authority occasionally receives reports from customers about “dirty” or discolored water coming from their tap. This discoloration—usually caused by naturally occurring iron and manganese particles—is aesthetically unpleasant and may lead to staining of laundry, but does not indicate that the water is unsafe to drink. The particles get stirred up when velocities increase in the water lines due construction, maintenance, or fire department use at hydrants.
Reporting “Dirty” Water
Anyone who experiences “dirty” water coming from their faucets is encouraged to do a whole-house, cold-water flush for five minutes. The best way is to start at the front hose bib. If the water clears up at the front bib after a few minutes, you will be able to clear the house by flushing all the cold-water taps inside front to back. If water does not clear at the front hose bib, there may be a main line issue and customers should contact Water Authority Dispatch at 505-842-WATR (9287), Option 1.
The NO-DES Process
If doing a whole-house flush does not solve your “dirty” water problem, the NO-DES truck may be deployed. It works by connecting two hydrants in a temporary loop to clean the pipe. Some 1,400 feet of NSF (National Sanitation Foundation)-rated 6-inch lay-flat hoses are deployed with hydraulically operated hose reels and then connected to the hydrants. Pressurized water is then circulated in the loop with enough velocity to scour the pipes between the two hydrants. The NO-DES truck can flush several city blocks from one hydrant by manipulating isolation valves to create loops or circuits. During the circulation, all the water is routed through filter vessels capable of removing any particle down to one micron in size (for reference, the width of an average human hair is about 70 microns).
A Water Authority Utility Technician always monitors the NO-DES control panel for the amount of water flowing (gallons per minute), the filtering system, and turbidity (cloudiness) levels which indicates when the filters need to be changed. Technicians use turbidity as a benchmark to ensure that the flushing process is complete. The temporary loop is then disconnected, never disrupting the water service for nearby customers.