Preparing Your Building for Reopening

This post was originally published on April 28, 2020.

State and local Stay-at-Home Orders have changed the way our communities shop, eat, do business, and go to school. When buildings are vacant or operating at significantly reduced capacity for a long period of time, the water that would flow every day is left sitting in the pipes and devices. Disease-causing microorganisms, like the one that causes Legionnaires’ disease, can begin to grow. Corrosion control can be impacted. To make sure that you remove any stale and potentially unhealthy water in your building’s system, we are asking you to follow these steps as you prepare to reopen your property to employees and customers.

The key to preparing your facility is to flush the water systems and devices. For larger buildings, a single flush isn’t enough to re-establish good water quality, so it’s important to plan ahead and include flushing as a part of the cleaning and routine maintenance that will have to be completed before reopening. This also protects the health of any staff or occupants still working on the premises. We recommend performing a final flush in the 24 to 48 hours before a building officially reopens.


Flushing in stages is best. Begin at the main service line and include all the plumbing, storage tanks, fixtures, and equipment such as water fountains and ice machines. The first flush pulls out stale water, while follow-up flushes ensure fresh water with disinfectant is drawn fully through the building. The longer service is interrupted, the more flushing is needed.

Consider the following steps when flushing your facilities:

  • Flush all faucets (remove faucet aerators, if possible) for 10 to 30 minutes.
  • Open all outlets at once to flush the service line and then open them again, individually, starting near where the water enters the building.
  • Flush cold water first. Then flush hot water until it reaches its maximum temperature.
  • Follow manufacturer recommendations to flush water fountains, hot water tanks, hot water recirculating loops, ice makers, dishwashers, humidifiers, and cooling towers.

Please consider capturing and reusing the flushed water for outdoor watering or cleaning purposes. There is no evidence that the coronavirus can survive in treated drinking water.

More Information

Flushing pipes is a precaution that should be taken after any shutdown of more than a few days. Depending on the complexity of a building’s water system, facility managers should develop a comprehensive water management program for this process, but it should not replace a facility-specific Water Management Plan.

The existence of disinfectant at an outlet is a good proxy to help you determine if flushing was adequate to restore fresh water to the building’s water system. OWASA will provide facility managers with test strips to assess the effectiveness of flushing. Please contact us at to request chlorine test strips.

Frequently Asked Questions (FAQs)

Why do pipes and devices need to be flushed in businesses, schools, or commercial buildings that were closed for the Stay-at-Home Order?

Water that sits in pipes becomes stale when buildings are vacant or operating at drastically reduced capacity for a long period of time. Harmful pathogens like the one that causes Legionnaires’ disease can grow in unused water tanks, hot tubs, and cooling towers and lead to a wave of waterborne illness across the community.

But water is disinfected to prevent pathogens like the one that causes Legionnaires’ disease. It was safe a month ago, what changed?

The chlorine and ammonia added to disinfect the water at the water treatment facility begin to dissipate over time. Without them, microorganisms can grow in pipes, fixtures, and tanks.

What devices need to be flushed?

Any device that water passes through needs to be flushed. This includes: water fountains, ice machines, soda machines, water heaters, dishwashers, and coffee makers. Replace all point-of-use filters, including the filter in refrigerators. Keep water heaters set at their designated temperature (ideally at or above 120°F). Continue routine maintenance on hot tubs and swimming pools.

What would happen if buildings just reopened and used stagnant water?

This is an unprecedented event for the plumbing systems in many buildings. Pathogens in stagnant water could lead to a wave of waterborne illness across the community. That’s why it’s vital to flush the stale water out before the buildings reopen.

What do medical experts say about this risk?

The Centers for Disease Control and Prevention (CDC) has published an online checklist to help determine a building’s risk of having problems with water quality after sitting unoccupied for several weeks. It includes questions about whether the building has a centralized hot water system, is taller than 10 stories, or has a cooling tower, hot tub, or decorative fountain.

How can we make sure our building’s water is safe before we reopen for business, education, or other purpose?

The CDC is offering guidance with eight recommendations that include: developing a comprehensive water management program; making sure your water heater is properly maintained and the temperature correctly set; cleaning all decorative features such as waterfalls or fountains; ensuring hot tubs and spas are safe for use; cleaning safety equipment such as eye wash stations and safety showers; checking with your local utility to request a water quality check; and flushing your building’s water system.

What makes up a building’s water system?

A building’s water system starts at the meter and continues through the owner’s service line into the building. It includes all the building’s plumbing, storage tanks, and fixtures, including fire suppression systems.

What does flushing involve?

The American Water Works Association recommends a thorough flushing process that includes running water through all faucets and spigots for anywhere from 10 to 30 minutes. Flush the cold water lines first and then the hot water lines. Run the water in one direction, from the building’s entrance to its outer points. Flush all water-using appliances like ice machines and dishwashers. Flushing for a longer period of time or more than once may be necessary. Any piece of equipment where water is stored should be drained and flushed with cold water. Water treatment devices like filters and water softeners also need to be cleaned and flushed. The sooner you can start this process the better.

Is flushing all that’s needed?

That’s one step in the process for reopening. But every building is different. It’s important to take an inventory, examine the parts of your water system, and coordinate a specific plan to address every section where water may have collected during the stay-at-home period. Inspect mechanical equipment such as cooling towers, boilers, pumps, and backflow preventers. Clean showerheads, faucets, and anything else that sprays water and could send bacteria into the air. If your business caters to a clientele that includes people who have chronic health conditions or are immunocompromised, collect water samples and deliver them to a laboratory for analysis.

What buildings should flush their water systems?

These recommendations are for larger buildings such as hotels, offices, stores, restaurants, churches, college campuses, and schools. But experts say it’s always smart for small businesses and homeowners to protect themselves from waterborne diseases. Make it part of your regular routine. That means following local and state guidelines for household water use and following manufacturer’s instructions for cleaning, disinfecting, and maintaining any device or appliance that uses water.

Will I have to pay for the water?

The responsibility for maintaining water quality in a facility falls to the property owner or property manager. Water used for flushing can be captured and used for other purposes like outdoor watering or cleaning measures that would be needed before any facility would reopen. OWASA is offering chlorine test strips to measure water quality and ensure proper flushing has occurred. You can request test strips by emailing

More Questions?

Contact Katie Harwell, Water Treatment Plant Laboratory Supervisor, by email or calling 919-537-4227.