Reopening facilities for a post-COVID-19 world

As the COVID-19 outbreak slowed down and companies started eyeing a return to normal, a number of new and different risks have been emerging, including concerns about reopening dormant buildings with stagnant water systems.

Several weeks of zero-flow, lowflow and tempered water can result in microbiological growth, the leeching of heavy metals, and corrosion issues within plumbing systems, but there are steps that can be taken to maintain water quality and safety in plumbing systems of unused, or slightly used, buildings.

The flushing of the plumbing system is one of the first steps that should be undertaken to make a building safe for returning users.


Why flush?

Flushing is important because it clears out the low-quality water that has accumulated during the low-use period and replaces it with high-quality water from the municipal supply. This fresh water helps mitigate loss of protective scale as well as biofilm growth that may have emerged while the water was stagnant.

These conditions need to be addressed because they proliferate the growth of Legionella and other waterborne pathogens, creating a high-risk environment for those with compromised immune systems.

Proper flushing is a multi-step process that includes an initial flush, sequenced flushing, cleaning of fixtures and equipment, testing and monitoring, and any additional flushing that may be needed.

It’s vital to flush the entire piping system from point-of-entry to point-of-use, paying particular attention to the parts of the water system that have the greatest opportunity to make people sick. These include:

  • Faucets used for drinking water or food preparation;
  • Drinking fountains;
  • Ice machines and refrigerators with ice makers;
  • Showers;
  • Kitchen sink sprayers;
  • Water features that generate aerosols (fountains, spas, etc.); and
  • Parts of the water system used by children, the elderly and other susceptible people.


Quick Tip:

Prior to flushing, appropriate training for staff should be completed and PPE (personal protective equipment) should be provided.


The best time to start is now

Initial flushing and cleaning must be completed before resuming normal building operations. The sooner flushing is begun, the better. If possible, have staff start flushing now, even if the building’s reopening date is still unknown. The earlier a flushing regimen is initiated, the sooner the water quality will return to normal.


How to flush a system

Flushing requires an initial flush to get low-quality water and contaminants out, as well as follow-up flushes to help bring the building back to pre-COVID-19 water quality. Ongoing flushing draws particles through and out of the system and brings in disinfectant from the municipal system that can help control biological growth.

The longer service is interrupted, the more effort will be required for restoration.

Flush zone-by-zone, starting with the zone closest to the building’s water supply. In each zone, start with the cold water plumbing first, followed by the hot water. Within the zone, open taps starting with the outlet closest to the zone origin, working toward the farthest point. Flushing should not end until the farthest point-of-use tap has flushed for a minimum of five minutes, and the cold water temperature at the most distal tap is constant.

In order for flushing to be most effective, consider the following:

  • All valves should be in a fully opened position during the entire flushing process;
  • All aerators should be removed. If continued use is planned, clean or replace the screens prior to reinstalling the aerators;
  • Showerheads and faucets should be disinfected and sterilized. Consider replacing outlets if vulnerable populations have access; and
  • Prior to operating the system after flushing, adjust valves back to normal operating positions.

As part of the flush, all locations where water is stored should be identified, drained and flushed with clean cold water. This may include humidifiers, ice machines and dishwashers.

Many buildings have some form of water treatment in their plumbing system. Filters and water softeners should run as normal and be included in the flush. They should not be bypassed.

Once flow has returned after this initial flush, all hot water tanks should be drained. Temperature should be maintained, and the heater should not be turned off. Continual operation is important to prevent microorganisms from growing. Make sure that water heat storage temperatures are sufficient to kill bacteria (131°F to 140°F).

Twenty-four hours before reopening the building, it’s recommended to conduct a round of checks. Bring the hot water system back up to 140°F. Open all outlets and flush until they reach a minimum of 131°F. After flushing, conduct a final round of sampling to ensure there is no contamination.

After the building reopens, ongoing flushes should be scheduled since continual flushing help to repair destabilized scale and minimize biofilm growth. It is recommended that flushing be continued for a minimum of 12 weeks.

With best practices recommending ongoing flushes for a number of weeks after the initial system purge, ensure that the plan for your customers includes the opening of each point-of-use tap at least once per day and the flushing of the entire building once per week during ongoing flushing.

Unlike with the initial flush, it is not necessary to drain water storage during ongoing flushing, but continue to flush the cold and hot water systems separately, with the cold first and hot second.


Know the system & follow a logical sequence

If one isn’t already in place, create a map of the building’s plumbing system. Before the initial flush, sketch out the building water system to identify low-use water outlets, and then map out a flushing regimen in a unidirectional process. In large buildings, the water supply is often designed in zones and branches, such as different wings. Typically, each wing or set of branches will be served by the same riser.

Always start from the outlet nearest the water supply and proceed to the most distal outlets. Along this route, the flushing regimen should include the entire recirculating loop, both cold and hot water, all associated equipment and appliances, and all outlets including faucets, showerheads, eye wash stations, ice machines, hot tubs, therapy pools, and water features.


By: Jana Summey and Michael Breault