Flush Plumbing When Returning to Closed Building
Many businesses, schools, homes, and other buildings have been unused for several weeks due to the COVID-19 pandemic. When returning to a closed building, the stagnant water inside the building’s plumbing system needs to be flushed to replenish with fresh water. Under normal use, water pipes maintain a residual chlorine disinfection to protect the public health and aesthetic water quality. Water in unused buildings can degrade and cause health hazards such as Legionella growth and leaching of lead and copper from plumbing pipes.
Recommended flushing procedures for restoring water to unused buildings:Remove or bypass devices like point-of-entry treatment units prior to flushing.
1. Remove or bypass devices like point-of-entry treatment units prior to flushing.
2. Take steps to prevent backflow or the siphoning of contaminants back into plumbing (e.g., close valves separating irrigation systems from home plumbing, disconnect hoses attached to faucets, etc.)
3. Organize flushing to maximize the flow of water (e.g. opening all outlets simultaneously to flush the service line and then flushing outlets individually starting near where the water enters the structure).
4. Run enough water through all outlets (e.g., hose bibs, faucets, showerheads, toilets, etc.), removing aerators when possible. Typical durations in existing protocols range from 10 to 15 minutes during simultaneous flushing (duration varies based on outlet velocities).
5. Flush the cold water lines first, and then the hot water lines. Note: the hot water tank can be drained directly; it can require roughly 45 minutes to fully flush a typical 40-gallon hot water tank.
6. Replace all point-of-use filters, including the filter in refrigerators.
7. Additional precautions may be warranted if there is excessive disruption of pipe scale or if there are concerns about biofilm development. Actions that might be warranted include continued use of bottled water, installation of a point-of-use device, or engaging a contractor to thoroughly clean the plumbing system.
For further information about health issues related to stagnant water and how to ensure your building is safe:
- US Centers For Disease Control and Prevention: Guidance for Building Water Systems: https://www.cdc.gov/coronavirus/2019-ncov/php/building-water-system.html
- Environmental Science, Policy & Research Institute: Building Flushing Guidance After Coronavirus: https://esprinstitute.org/coronavirus-building-flushing-guidance/