Maintaining Water Quality in Buildings During COVID-19 Response

The Philadelphia Water Department urges owners and operators of dormant buildings to flush building water systems while closed and before reopening.

Water sent to all buildings is safe to drink and quality is not impacted by the virus causing COVID-19.   

However, buildings of any size that have been closed or used less frequently for an extended period of time may experience problems with water quality due to stagnation, or old water sitting in pipes. 

Property owners are responsible for ensuring the water in their building is safe.
Reopening should include a plan to address the water quality risks in dormant buildings.

The Pennsylvania Departments of Environmental Protection (DEP) and Health (DOH) issued guidance stating that flushing pipes and plumbing systems can help ensure your property is safe and ready for use once you reopen. Below are some steps property owners should consider including in reopening plans.

Building owners and tenants should take the following actions to reduce risks associated with stagnant water:

  • Run water from all outlets which dispense water at least weekly. The goal is to replace all stale water in the building pipes with fresh water from the source to every possible outlet. Follow this Environmental Science Policy & Research Institute guide on how to flush the water in your building.
  • Flush cold water lines before hot water lines.
  • Check your hot water system. Set your hot water heater to at least 120°F. Run the hot water tap until it reaches its highest temperature.
  • Take the proper steps before reopening. Follow the CDC’s eight steps to take before your business or building reopens

Note: It is important to take these steps even if you do not drink the water in your building.

Use appropriate protective equipment if those flushing outlets could breathe in water droplets or mist.

Legionella bacteria, the cause of Legionnaires’ disease, is spread through breathing in mist and small droplets, which can occur when a faucet is running at high-flow volume or in showers.

Who should take these precautions?

Any building not in use for more than one week. Properties managed as large campuses, like business parks and colleges, should also be considering this CDC guidance.

What problems are caused by unused water systems / plumbing?

Prolonged water stagnation can make water discolored or unsafe because of issues such as:

  • Elevated lead and copper levels
  • Growth of microorganisms, including dangerous Legionella bacteria
  • Disinfection byproducts

Legionella bacteria and other pathogens grow in plumbing over time, as disinfectant added at treatment plants slowly loses its ability to keep water safe.

What needs to be flushed? 

Restarting building systems safely requires flushing all plumbing and devices that use water.
Any devices that store or use water should be flushed. Examples include:

  • Ice machines and refrigerators that dispense water and ice
  • Water fountains and decorative fountains
  • Water heaters, storage tanks, and any droplet or mist-forming devices, such as cooling towers, and humidifiers
  • Eye-flushing devices, and certain medical and manufacturing devices and process equipment
  • Kitchen taps, bathroom taps, laundry and utility sinks, bar sinks, bathtub taps, and showerheads

Where possible, remove aerators before flushing. After flushing is completed, clean aerator screens and place aerators back on the faucet.


PWD does not provide testing of water quality for businesses and buildings. However, laboratories certified by the Pa. Department of Environmental Protection can provide these services.

Find more information at or contact the Southeast Regional Office: (484) 250-5900

Building managers can perform tests of total chlorine residual levels using commercially available testing kits. A measurable total chlorine residual should be detected at each outlet to demonstrate that flushing is complete. Only kits measuring “total” chlorine residual should be used.


The Philadelphia Water Department is here to help. Call our hotline for emergencies at (215) 685-6300, or email for non-emergency questions. The Water Department cannot assist with plumbing and water quality inside buildings or on private property.

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