Flushing Water Lines After Extended Shutdown

Business Resources

Important Guidance: Flushing Water Lines in Facilities After Extended Shutdown

This guidance applies only to buildings and facilities that have been shut down for an extended period without water use or where water was only sparsely used for a prolonged period of time.

Facilities that are re-opening 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; especially hotels, facilities that serve vulnerable populations, restaurants, and other large facilities that have shut down for an extended period.

Flushing your water system is important because when water is not drawn through a plumbing system over an extended period, the water becomes stagnant. Some larger service connections, including businesses and commercial buildings, may have shut down or significantly reduced their water use after the Sonoma County Shelter in Place Order went into effect on March 18, 2020. 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 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.

The City of Cotati is working around the clock to ensure you receive high water quality at your meter, but you are responsible for your water system in your facility. The public water system has remained pressurized and fully operational since the Sonoma County Health Order requiring residents to Shelter in Place was issued. The City of Cotati continues to conduct routine water quality sampling and analysis throughout the water distribution system on a weekly basis.

For questions about your water quality, please email Jon Caldwell or call them 707-665-3638

Recommendations for Flushing Your Private Water System

  • 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 fillers, 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.
  • 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.

Additional Considerations

  • End Point Devices - Another best practice, especially for schools and daycare facilities, is the removal and cleaning of end-point devices such as faucet aerators and drinking fountain filters. This is particularly important if any disruption of supply pressure occurred or is suspected while the building was shut down. Pressure disruptions can dislodge particulates, including lead, which can get trapped in aerators and filters, spiking lead levels and reducing water quality.
  • Water Treatment Systems and Drinking Water Filters - If there are water treatment or filtration products used in the plumbing system, such systems may need to be regenerated and flushed. It's possible for bacteria to grow in water filters under stagnant water conditions so replacing water filters is highly recommended. Always consult and follow manufacturer disinfection procedures and recommendations.
  • At-risk Populations - For all buildings serving high-risk populations, consider testing for Legionella at least seven days prior to re-opening the building. Water samples for testing should be collected after taking the remedial steps recommended above.
  • Protecting Water System Rehabilitation Personnel - Personnel working to rehabilitate stagnant water systems will be at some risk and should be advised to take precautions. Wearing proper Personal Protective Equipment (PPE), including safety goggles, rubber gloves and NIOSH-approved N95 facemasks, if available, are recommended best practices.
  • Other Building Water Systems - It's important to also check all other water systems in a building, such as water reuse systems, decorative water features such as fountains, and landscape irrigation systems. Follow manufacturer recommendations for disinfecting all water systems after periods of non-use. Additionally, this is a good reminder that large facilities should ensure that all plumbing is well maintained, and that emergency safety equipment including fire sprinkler systems, eye wash stations, and safety showers are also clean and well-maintained.
  • Floor Drains - If the building has floor drains, be sure to pour water into the drain to make sure that the trap is fully restored in order to keep sewer gases from entering the building. Functioning drain traps also protect occupants from health risks and need to remain "wet".

Further Guidance for Businesses and Commercial Buildings that have Shut Down