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Flush building pipes when reopening

Updated: Aug 4, 2020

DU advises flushing plumbing to remove stagnant water in commercial buildings when reopening after extended closure.

Closing buildings and businesses for weeks or months reduces water usage, potentially leading to stagnant water inside building plumbing. This water can become unsafe to drink or otherwise use for personal or commercial purposes. Types of buildings/businesses affected include churches, day cares, offices, restaurants, and schools. EPA recommends that commercial building owners, building managers, and businesses take steps to flush the building’s plumbing before reopening. Flushing involves opening taps and letting the water run to remove water that has been standing in the interior pipes and/or outlets. The flushing time can vary by the plumbing configuration and type of outlet being cleared. Flushing may need to occur in segments (by floor or room) based on the building’s plumbing design and water pressure. Begin nearest to where water enters the building and move toward the farthest tap. Cold water should be flushed before hot water. Consideration should be given to completing the following minimum preventative measures:

  • All cold water outlets should be flushed before hot water.

  • Flush hot water outlets until water reaches its maximum temperature.

  • Flush cold and hot water at all points of use (indoor and outdoor faucets, toilets, drinking fountains, and water using devices such as dishwashers, refrigerators/ice makers) to replace the water that has been standing in the pipes during the period of non-use.

  • Water-using devices may require additional cleaning/disinfection steps in addition to flushing, such as changing water filters, draining and flushing hot water heaters, and discarding ice. It is important to follow all manufacturers recommended cleaning procedures.

  • Consider checking water quality parameters, such as temperature, pH, and disinfectant levels, in the water entering the building and at points of use after flushing to verify that fresh water is being flushed through the entire plumbing system. Achieving stable temperature, pH, or disinfectant levels can be a good indicator that the system has been adequately flushed.

  • Large water using appliances should run through at least one full cycle prior to use.

  • NOTE: Flushing complex or multi-floor plumbing systems should be done by a professional plumber.

More information and additional resources may be found at and If you have questions or concerns regarding your water quality, please contact DU at 256-552-1444.

DU Plumbing Flush Notice 7-30-20
Download PDF • 481KB

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