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Water Main (pipe) Flushing FAQs

Why is there water running down the street?

Even though you may not see Denver Water employees on your block, you may see water running down the street from a site several blocks upstream. There are several reasons why you may see water running down the street: 

  • Flushing: Denver Water may be flushing water pipes, or water mains, in your neighborhood to help maintain water quality. Water is purged out of the water main by opening fire hydrants or “blow-off” valves in dead-end streets, cul-de-sacs and pressure zone boundaries. Denver Water may also be flushing hydrants when requested by fire departments or insurance companies to ensure adequate flow for fire protection. 

  • Installing or replacing a pipe: Denver Water crews install or replace an average of 80,000 feet of pipe per year, with the goal of replacing 140,000 feet of pipe per year by 2026. Replacements are done for various reasons, including repairing or preventing main breaks, replacing corroded pipe, alleviating water quality concerns, increasing available hydrant fire flow and improving overall area delivery. Flushing the water main is part of the disinfection process for the newly installed or repaired water main. 

  • Leaks: There may be a leak, such as a pipe break or service line leak, in your neighborhood. If that is the case, please be assured that Denver Water is responding. We provide emergency response 24 hours a day and will repair the leak as quickly as possible.

Why does Denver Water need to flush water pipes?

During the winter, when water use is generally at its lowest, water sits at dead ends, cul-de-sacs and pressure zone boundaries in the system and can become stale and lose its disinfectant content. 

Denver Water adds disinfectant to its treated water to prevent any potential bacteria from growing in the system, so it’s important to flush out those areas before the disinfectant levels drop below minimum standards. 

The word “stale” is frequently used to describe the taste and odor occasionally associated with the water in these low-flow areas. The longer the water sits in the water pipe, the more minerals are absorbed from the pipe. Some minerals are necessary to prevent direct contact between the water and the pipe; however, they can become a nuisance in larger amounts. Minerals will continue to build up in the water pipe if left unattended and will eventually impede water flow for fire protection, as well as cause taste and discoloration issues. Flushing helps remove this buildup.

Should I use water while pipes are being flushed?

While mineral buildup can become a nuisance and potentially cause discoloration and issues with taste and odor, they are completely harmless. Your water is safe to drink. 

If you notice discolored, or “dirty” water, you should avoid using hot water (including laundry or running your dishwasher). Instead, run your cold water from a laundry sink, bathtub or, preferably, an outside spigot until the water runs clear. 

You may want to flush your hot water tank by opening the valve at the bottom of the tank. If you are doing laundry, consider rewashing them before drying, which usually removes any minerals that may have been deposited.

Can I collect water at flushing sites for my own use?

Residents in homes near a flushing location may work with on-site staff to recover some flushed water from the street for use in irrigation. However, because of high water pressure directly out of the hydrants, residents cannot collect water directly from the flushing nozzle.