Flushing Water Lines in Facilities


Flushing Water Lines in Facilities

After Extended Shutdown

Facilities that are reopening after an extended shutdown should take precautionary steps for water quality, including but not limited to flushing your plumbing fixtures before resuming normal operations. This is important for all businesses, and especially hotels, facilities that serve vulnerable populations, restaurants, and other large facilities that have shut down for an extended period.

A complete shutdown or significant reduction in water use may compromise water quality in a customer’s connected plumbing and fixtures; including pipes, appliances, and heating and cooling systems. During extended periods of no or very little water use there is the potential for depressurization, loss of disinfectant residual (this can result in the growth of harmful pathogens and microorganisms, such as Legionella), and the leaching of metals. Individuals at the highest risk of becoming ill from such pathogens are the elderly and those who are immunocompromised.


  • Flush Water System for at Least 10 Minutes – All water systems in buildings that have been vacant or sparsely utilized for weeks or months must be thoroughly flushed. Start with the outlet(s) at the greatest distance from your service connection (water meter) and let it flow for a minimum of 10 minutes. Flushing for longer may be needed for larger water systems. The purpose of flushing is to replace all the water inside building piping with fresh water.
  • Flush Each Water Fixture for at Least 5 Minutes – After flushing the entire system for 10 minutes, flush hot and cold water, as applicable, through all points of use (e.g. sink faucets, toilets, drinking water filters, showers, etc.) for at least five minutes. This will clear any stagnant water in individual plumbing fixtures.
  • Important Safety Precautions – Stagnant water is likely to contain higher levels of Legionella and other pathogens. Personnel flushing the water system are advised to open outlets slowly, to avoid splashing and the creation of aerosols.
  • Ice Makers – Dispose of old ice and flush the water supply to the ice maker.
  • Large Facilities – Flushing may need to occur in segments (e.g., floors or individual rooms) due to facility size and water pressure. For buildings with internal controls, operate all valves in the fully open position so that any particulate matter can be flushed through. Pay close attention to float-operated or other restrictive valves which need to be manually opened to clear particulates and prevent fouling of the valves. Adjust valves back to normal operating positions to ensure that the system is rebalanced.
  • Frequent and Regular Flushing – Facilities that have staff onsite should consider flushing water systems for shorter periods, if performed on a regular basis, such as every three to four days.