Water Flushing After Building Closures

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Stagnant water in a building's plumbing systems can cause serious water quality problems

Water stagnation can lead to the growth of disease-causing bacteria, such as Legionella.

 If a building has been unoccupied or has low water usage due to staff reductions for a week or longer, the old water needs to be flushed out of the system to restore water quality.


Letrunning faucet's Get the Water Moving Again!

  • Open all cold water faucets, starting with the ones closest to where the water service enters the building, and let run—simultaneously—for 15 to 30 minutes.
  • Open hot water faucets and let run until cold. Alternately, if possible, drain hot water tanks directly.

  • Be sure to flush all water-using appliances, such as ice makers, coffee machines with direct water lines, and dishwashers.
  • Replace all filters and clean aerators attached to faucets. 
  • You may need to bypass any water treatment systems, like water softeners, to ensure effective flushing.


Ideally, a building’s water should be flushed once a week while the building is unoccupied.

Flushing must be done prior to reopening the building!


Water Flushing Resources

Recharging Your P-Traps

P-Trap DiagramIn addition to flushing stagnant water out of your building's pipes, you may need to recharge your P-Traps to prevent sewer gas from coming into your building.

While your building was empty or partially occupied during COVID 19 related shutdowns, the sanitary drainage system and its fixture traps may have been affected by evaporation. Commonly known as P-Traps, these plumbing fixture traps are designed to prevent sewer gas from entering the building through the network of drains. In addition to flushing the building’s water system, these plumbing fixture traps may need to be replenished with water. Building owners or managers can replenish by simply running the faucet on a sink or lavatory. To make sure floor drains, floor sinks or other waste receptor traps are replenished, simply dump water into these floor drains or other waste receptor to recharge the trap water seal.