Water quality can be seriously compromised when it sits in building plumbing systems for extended periods of time without movement. As buildings close and reopen during the COVID-19 pandemic, it is important to keep in mind how prolonged periods of little to no water usage can negatively impact water quality, creating the potential for serious health concerns if proper flushing and reopening procedures are not followed.
To protect public health, building owners and managers should minimize water stagnation during closures and maintain building water quality prior to reopening. Maintaining water quality may help prevent the need to perform more complex restoration steps. The Department of Public Health recommends the following steps to help mitigate risks and provide a safe water supply.
The purpose of flushing the water throughout the facility is to replace any residual and potentially stagnant water in the plumbing with fresh water. Flushing involves opening taps and letting the water run to remove water that has been standing in the interior pipes and/or outlets. Prior to doing any flushing at your building, ensure the water heater has been properly maintained and set to at least 140 degrees Fahrenheit to further prevent the growth of Legionella. Follow the manufacturer’s instructions to determine whether the unit needs to be fully drained after prolonged periods of low use.
Clean all water features, safety equipment and sources of non-drinking water (decorative fountains, safety showers, eyewash stations, fire sprinkler systems, etc.). Follow any manufacturer’s instructions for flushing, cleaning and disinfecting these items. Ensure there is no residual slime or biofilm.
Cooling towers - towers and basin should be cleaned and free of slime or biofilm. Ensure that the cooling towers are maintained (including start-up and start down procedures) per manufacturer’s instructions and then proceed with disinfection. For further information, consult CTI guidance.
Spas: Drain, clean and disinfect any hot-tubs or spas. Flush water at source point prior to refilling. Follow the CDC’s recommendations for hot tub and spa disinfection (follow Steps 4–9 and 12–13).
Consider creating a water management plan. The CDC provides a toolkit to assist in creating an ideal water management plan.
Check in with your local water utility (Missouri American Water) to learn if there have been any recent water supply disruptions or to request a check on your disinfectant residual entering the building. After thoroughly flushing the building and achieving optimal water quality, regularly check your water parameters (temperature, pH, disinfectant levels) and follow your water management plan to ensure adequate protection against Legionella.