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Flushing Water Mains

Why is there water running down the street in front of my house?

There are several reasons why you may see water running down the street.

  • Flushing — Denver Water may be flushing water mains in your neighborhood. We do this once a year according to an annually scheduled maintenance plan to help maintain water quality. Water is purged out of the water main by flushing fire hydrants or drains in dead-end streets, cul-de-sacs and pressure zone boundaries. Denver Water may also be flushing hydrants upon request by fire departments or insurance companies in order to ensure adequate flow for fire protection.
  • Installing or replacing a water pipe — Denver Water crews install or replace an average of 60,000 feet of pipe per year. Replacements are done for various reasons, including repairing or preventing main breaks, replacing corroded pipe, alleviating water quality problems, increasing available hydrant fire flow and improving overall area delivery. Many times these repairs and replacements require some flushing of water mains as part of the disinfection process for the new or repaired main prior to reconnecting the system.
  • Main break — There may be a main break 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 break as quickly as possible.

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.

Why does Denver Water need to flush water mains?

During the winter months, 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.

Because of limited use, the water sits in these dead ends and begins to slowly 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.

Stale also describes the taste and odor occasionally associated with the water in these low-flow areas. The longer water sits in the main, the more it can absorb the flavor of the pipe itself.

Minerals — iron (rust), calcium, magnesium and manganese — also build up in these low-flow areas. These minerals are necessary to develop a thin layer that coats the inner surface of the pipe to prevent direct contact between the water and the pipe, which allows water to absorb the pipe flavor.

However, the very same minerals that can help in a thin layer are a nuisance in larger amounts. They will continue to build up in the water main if left unattended and eventually impede water flow, which can lead to reduced water flows for fire protection and cause taste and discoloration issues. Flushing helps remove this buildup to keep water clean and safe.

How long does it take to flush a water main?

Usually Denver Water only needs to run water at these sites for a few minutes to clear out the mineral buildup, but occasionally more extensive flushing is necessary.

Should I use water while mains are being flushed?

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

However, if you are running water when we are flushing, you could get some dirty water. If this happened, you should not run your hot water or do any laundry. Turn on and run your cold water in a laundry sink or through an outside spigot until the dirty water clears out of your pipes.

You may also want to flush your hot water tank by opening the valve at the bottom of the tank. If you are doing laundry, do not dry the wet clothes. Rewashing them before drying will normally rinse any minerals that may have ended up in the load.

What steps does Denver Water take to conserve this water during a drought?

Our operations and maintenance team has prioritized Denver Water’s annual maintenance plan to reduce noncritical flushing during droughts.

Denver Water has tanker trucks that can be deployed to appropriate sites to capture flushed water and redistribute it to designated public landscapes in need.

Can I request the tanker truck come to my house and release recaptured flushing water?

Unfortunately, no. Denver Water has developed a schedule for tanker trucks based on capacity, location of flushing sites and high-priority public landscapes to ensure we use our resources as efficiently as possible to redistribute this water.

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.