Guest Blog: Reopening Schools – Drinking Water Concerns

After closing early and transitioning to online learning, school systems across the United States are trying to figure out if and how to reopen this fall. Amid the discussion about social distancing in classrooms and hallways, a critical component of school reopening plans may be taking a back seat: ensuring that the schools’ drinking water infrastructure, which may have been shut down for all of these months, does not expose children to new non-COVID-19 health risks.
Credit: Stacey Newman/iStock

Guest blog written by Joseph Manning

“My child is back in school. We understand the need to wear a mask and practice social distancing, but how can we know if the water is safe to drink when the school has been shut down for so long?”

Many parents are asking this question. After closing early and transitioning to online learning, school systems across the United States are trying to figure out if and how to reopen this fall. Amid the discussion about social distancing in classrooms and hallways, a critical component of school reopening plans may be taking a back seat: ensuring that the schools’ drinking water infrastructure, which may have been shut down for all of these months, does not expose children to new non-COVID-19 health risks.

Parents: Learn about these concerns and the safety precautions that can be taken regarding drinking water in schools and ask questions

This blog is intended to provide basic information on the risks inherent in reopening stagnant drinking water systems in schools. Parents can use this information to find out what their children’s schools are doing to ensure that the drinking water is safe. Schools can use this information to follow the work that their contractors are performing.

The ABCs of Drinking Water in Schools

When school buildings are not in use, water in the buildings’ plumbing becomes stagnant. This stagnation poses several public health concerns, particularly as it relates to drinking water that the children would be susceptible to:

  1. Microorganisms - Water is often treated with disinfectants, but as water sits stagnant, these disinfectants break down and stop functioning. Without disinfectants, microorganisms can grow in the buildings’ water systems. Also, when hot water sits stagnant, it can cool to the temperature at which microorganisms can grow. Depending on what microorganisms are present, these can cause dangerous respiratory infections, such as Legionnaires’ disease or gastrointestinal disease. See Centers for Disease Control and Prevention (CDC) latest guidance, Guidance for Reopening Buildings After Prolonged Shutdown or Reduced Operation, (updated May 7, 2020)
  2. Disinfection byproducts - As disinfectants dissipate, disinfection byproducts (DBPs) may accumulate in the water system. DBPs form when chlorine or chloramines, added as a disinfectant, reacts with organic matter naturally occurring in the water. There are hundreds of DBPs, including some that are regulated such as trihalomethanes and haloacetic acids; EPA and CDC have concluded that some of these may cause cancer. See this CDC resource: Disinfection By-Products  and EPA’s disinfection byproducts summary.
  3. Lead - Plumbing and fixtures often contain lead. Lead in school water is already a challenge during normal water use and may be a concern even if there had not been a school shutdown. Water in many communities is treated to create a protective coating on pipes that reduces but does not prevent lead exposure. This coating destabilizes when water systems go unused. Absent the protective coating, lead can dissolve or flake off as particles in even higher quantities than normal. Lead is toxic and particularly harmful to children. See this resource: Environmental Science and Policy Research Institute, Building Water Quality and Coronavirus: Flushing Guidance for Periods of Low or No Use, 1 (April 3, 2020)

Flushing the School’s Plumbing Is Critical

The most effective way to address these concerns is by flushing a building’s water system prior to reopening. As discussed below, there are a range of flushing goals and strategies that schools can use, and they vary widely in terms of the amount of planning needed and the water quality outcomes expected. Parents and staff: find out from your administrators what the flushing goals and strategies are for your schools. 

Flushing goals can range from scouring sediment and biofilm buildup from indoor plumbing, to merely bringing fresh water into outlets used for drinking water. In general, flushing should use fresh water to push out old, stagnant water. Flushing should include all fixtures (faucets, hoses, drinking fountains, shower heads, water coolers, etc.) including appliances, such as dishwashers and ice machines. If possible, flushing should begin immediately and continue weekly until the resumption of normal, continuous use. However, for school buildings with lead fixtures, the flushing should begin at least 12 weeks prior to reopening, as that is how long it takes to re-stabilize the protective coating in pipes and fixtures. If children and staff are back at school before the 12-week period has concluded, they should bring their own water to drink, or the school should provide an alternative source of potable water.

The section at the end of this blog describes the general steps for most flushing strategies. Consult the resources below to explore specific flushing goals and whether they are appropriate for your schools.

Tips for Helpful Communication by Schools

These are stressful times. Schools should communicate with parents, students, and staff about the safety of school drinking water.

Here are some tips for information that schools can communicate to parents, students, and staff:

If water maintenance has not been happening, tell students and staff to:

  • Bring their own drinking water (or provide bottled water).
  • Not drink the water in the school until the school says it’s okay.
  • Wash their hands.

If water maintenance has been ongoing during the shutdown, tell students and staff what the school has been doing to maintain water quality and to:

  • Use designated outlets or bottle fillers for drinking water at school.
  • Feel free to bring their own water.
  • Wash their hands.

Steps for flushing a building:

Properly flushing a school water system involves several steps, from planning to regular follow up flushing. Facilities managers should carefully complete each step to restore and maintain a safe water system. Capturing this work in a School Water Quality Management Plan will allow schools to use this effort for years to come, resulting in long-term health benefits to students and staff.

  1. Develop a flushing plan: Schools should develop a comprehensive flushing plan. This means identifying the points of use (POU) (i.e. sink, shower, etc.), mapping the building’s water zones (branches of the building water system with a common source or parts of the building water system served by a common riser – vertical pipes that carry water between floors of a building), and identifying an individual responsible for ensuring that the flushing plan is properly implemented. Purdue University has produced a model school flushing plan, which contains some but not all of the steps found below.
  2. Clean fixtures: Schools should clean all drinking water fixtures. This includes decontaminating fixtures, removing and cleaning aerators (small, usually mesh screens at the ends of faucets, which reduce the volume of water flowing from the faucet), and replacing filters. Aerators should remain off during flushing to maximize water pressure and flush out particles.
  3. Flush cold-water zone-by-zone: Begin with the zone nearest the building’s water supply (located at the meter) and with the POU nearest the zone’s origin. Open the cold water tap wide to flush. Calculate the volume of the service line and time the flushing so the service line is completely flushed before bringing any additional water through the building. Begin with the faucet nearest the origin then open each POU on the same branch until reaching the most distant POU. Flush until the most distant POU is open for at least 5 minutes and the cold-water temperature remains consistent. Continue to flush all zones moving outward from the meter.
  4. Flush hot-water zone-by-zone: Repeat the same process outlined in step 3, flushing the hot water in each POU. The water flushed from a fixture will initially be cooler than the maximum hot water temperature. Flushing should continue until the hot water reaches and maintains its maximum temperature.
  5. Continue flushing weekly for the next 12 weeks: Repeat steps 3 and 4 weekly. Twelve weeks is the approximate amount of time needed to re-stabilize the protective coating, so flushing must continue for at least this amount of time, even if the building reopens sooner.
  6. Open every POU daily: A water professional may also recommend that each tap in the building is opened at least once per day.

Additional considerations:

Water quality testing: Building managers should determine whether testing for contaminants, such as lead and microorganisms, is appropriate after flushing the system. The federal EPA does not require testing for lead or microorganisms in schools (except in unusual cases where the school has its own water system that produces its own water). EPA does, however, provide voluntary guidance for testing for lead in drinking water in school buildings in the 3Ts for Reducing Lead in Drinking Water Toolkit.

Very few states in the United States require schools to test for lead in drinking water in schools. NRDC has developed a model law that would mandate the placement of filters to remove lead from drinking water in schools, followed by testing the water to ensure that the filters are working properly.

System disinfecting: In buildings that are prone to microbial growth and biofilms, including those with storage tanks and remote branches where stagnant water can accumulate, as well as those that serve large numbers of immunocompromised individuals, flushing may not prove adequate to disinfect the system. Managers of these buildings should consult with a water professional about administering chlorine shock treatments. Chlorine shock treatments disperse significant quantities of chlorine through a building’s water system to eliminate microbial growth. This should only be done in consultation with a water professional and after understanding how shock chlorine will interact with the building plumbing, including pipe material and various components (i.e. do not let shock run through the filters). See this resource: Canadian Water and Wastewater Association, Safely Re-Opening Buildings: A Fact Sheet for Building Owners/Operators, 6 (May 2020).

Hot water tanks: If possible, hot water tanks should be drained and allowed to refill, as they are a reservoir of large quantities of stagnant water in unused buildings. However, always ensure that hot water tank maintenance is carried out by a professional in accordance with the manufacturer’s instructions. Additionally, in order to protect against Legionella, set the hot water temperature to at least 140oF. See this EPA resource: Maintaining or Restoring Water Quality in Buildings with Low or No Use, 1, (May 2020).

Wear PPE: While performing all the activities previously discussed, staff should wear personal protective equipment (PPE), including mask, glove, and eye protection. N95 masks are advised because they are effective in protecting against aerosolized particles and microbes that can be produced when flushing.

Additional Sources – 2020 COVID-19 Related Flushing Guidance for Building Plumbing


Michigan Department of Environment, Great Lakes, & Energy – School guidance:,9429,7-135-3313_3675_3691-474608--,00.html

Purdue University – Example Procedure for Flushing an Actual School Building:

American Water – School & Business Reopening fact sheet:

U.S. Environmental Protection Agency – 3Ts for Reducing Lead in Drinking Water Toolkit:

New Jersey Department of Environmental Protection – Lead sampling guidance:

New Jersey Department of Environmental Protection – Overview Lead in Drinking Water at Schools Facilities:

Large buildings

Centers for Disease Control and Prevention – Guidance for Building Water Systems return to service – Legionella focus:

Environmental Science, Policy & Research Institute (ESPRI) and AH Environmental Consultants, Inc. (AH):

U.S. Environmental Protection Agency – Guidance for restoring water quality after non-use:

Canadian Water and Wastewater Association – Safely Re-Opening Buildings a Fact Sheet for Building Owners/Operators:

Proctor et al., Considerations for Large Building Water Quality after Extended Stagnation:…

Purdue University – Building plumbing restoration guidance (developed via National Science Foundation rapid response grant):

New Jersey Department of Environmental Protection – Drinking Water Flushing Guidance For Restoring Water Quality in Buildings with Low or No Use:

The Water Research Foundation – Flushing Guidance for Premise Plumbing and Service Lines to Avoid or Address a Drinking Water Advisory

Passaic Valley Water Commission:

Joseph Manning was a law intern in the People and Communities Program at NRDC during the summer of 2020. He is a third-year law student at Boston College Law School in Newton, Massachusetts.

Technical contributor, Elin Warn Betanzo, PE, Safe Water Engineering