Ensure the safety of your occupants and building water system and devices: Check for hazards including Legionella, mold, and lead and copper.

A temporary shutdown or reduced operation of a building (for example, a school or a childcare facility) and reductions in normal water use can create hazards for returning occupants. Check for hazards before reopening after a prolonged period of building inactivity. Hazards include Legionella (the cause of Legionnaires’ disease), mold, and lead and copper contamination pdf icon [PDF – 995 KB] external icon  from corroded plumbing.

For Legionella, a “prolonged period” may be weeks or months depending on plumbing-specific factors, disinfectant residuals, water heater temperature set points, water usage patterns, and preexisting Legionella colonization.1

For mold, a “prolonged period” may be days, weeks, or months depending upon building-specific factors, season, and weather variables.2

For lead and copper, a “prolonged period” may be hours, days, weeks, or months depending on plumbing and water-specific factors, the amount of time the water remains stagnant inside the pipes, whether there are protective scales or coatings present inside pipes that prevent metals from leaching into water, and the materials used to build the plumbing system.3

Note that additional hazards not discussed on this page may exist for returning occupants. These can include other hazards, such as nontuberculous mycobacteria, disinfection by-products, and sewer gases that enter buildings through dry sanitary sewer drain traps.

Stagnant or standing water in a plumbing system can increase the risk for growth and spread of Legionella and other biofilm-associated bacteria. When water is stagnant, hot water temperatures can decrease to the Legionella growth range (77°–113°F, 25°–42°C). Stagnant water can also lead to low or undetectable levels of disinfectant, such as chlorine. Ensure that your water system is safe to use after a prolonged shutdown to minimize the risk of Legionnaires’ disease and other diseases associated with water.

People at increased risk of developing Legionnaires’ disease, such as those with weakened immune systems, should consult with a medical provider regarding participation in flushing, cooling tower cleaning, or other activities that may generate aerosols. Wearing a half-face air-purifying respirator equipped with an N95 filter, or an N95 filtering facepiece, may be appropriate in enclosed spaces where aerosol generation is likely. Respirators must be used in accordance with a comprehensive respiratory protection program, which includes fit testing, training, and medical clearance ahead of their use (see OSHA standard 29 CFR 1910.134external icon  and OSHA Legionellosis websiteexternal icon ). For more information about N95 respirators, visit the NIOSH National Personal Protective Technology Laboratory (NPPTL) website.

Mold will grow on building materials where there is moisture, produced from leaks or condensation from roofs, windows, or pipes, or from a flood. Mold can grow on a variety of surfaces, such as ceiling tiles, wallpaper, insulation, drywall, carpet, and fabric. People with asthma and other respiratory conditions and those with mold allergy or weakened immune systems should avoid buildings suspected or confirmed to have mold contamination. Ensure that your building does not have mold after a prolonged shutdown to maintain a safe working environment for returning occupants.

Content adapted from the National Institute for Occupational Safety and Health [NIOSH] Heating, Ventilation, and Air Conditioning [HVAC] Cleaning and Remediation guidance.

Additional information and CDC guidance on controlling dampness issues that result in indoor mold growth, as well as on renovation and remediation if indoor mold has become an issue is available from NIOSH.

Metals, such as lead and copper, can enter drinking water in a building from corrosion of a building’s plumbing (pipes, fixtures). Corrosion is a chemical reaction that dissolves or wears away metal from pipes and fixtures. Corrosion may occur during long periods of low or no water use, leading to potentially high levels of lead or other metals in the building’s drinking water. Lead is harmful to health, especially for children, as there is no known safe level in children’s blood.  For more information on corrosion and how lead gets into water, visit CDC’s Lead in Drinking Water webpage or EPA’s Basic Information About Lead in Drinking Water website.external icon

Additionally, water sitting stagnant (not flowing) in the pipes can make the water chemistry more corrosive over time and use up any corrosion control chemicals added by water utilities to limit the release of lead and copper. This may further disturb protective pipe scales or coatings inside plumbing materials. If pipe scales are disrupted, lead and copper could continue to be released at higher levels until the scales are restored after the building returns to normal operations.

To prevent high levels of lead and copper in the drinking water while there is low or no use of the building, follow EPA’s Maintaining or Restoring Water Quality in Buildings with Low or No Useexternal icon  guidance. This guidance has strategies to maintain the water quality in the building and prevent water stagnation. Maintaining water quality will flush potentially corrosive water and disrupted pipe scale containing lead out of the pipes. It will ensure fresh water containing proper levels of corrosion control chemicals is brought into the building and help restore any disrupted pipe scales prior to building opening.

Take additional steps to reduce lead and copper in drinking water. Preventing stagnation does not completely prevent the release of lead into drinking water and may require additional steps, including:

Contact your water utility if you’d like to receive a copy of their latest annual drinking water quality consumer confidence report. More information and ways to locate these reports is available from EPA.external icon   If your water comes from a private well or water supply, check with your health department for information on water quality in your area.

If you are served by a water utility, they may test your water upon request.  You may also contact laboratories certified to test for lead in water. For information on locating these laboratories, see EPA’s list of laboratories included in the National Lead Laboratory Accreditation Program.external icon

Use only cold water for drinking and cooking. Water that comes out of the tap warm or hot can have higher levels of lead. Remember, boiling water does not remove lead from water.

Regularly clean faucet screens (also known as aerators). Sediment, debris, and lead particles can collect in your aerator. If lead particles are caught in the aerator, lead can get into your water.

If you use filters, make sure they are certified to remove lead. Follow manufacturer instructions for installation and maintenance. Replace filter cartridges before they expire to maintain their effectiveness. Do not run hot water through filters. Find more information about choosing a filter certified to reduce lead on EPA’s website.external icon

1 For example, a building potable water system with extensive dead-legs, low disinfectant residuals, tepid hot water temperatures, minimal water flow, and an established Legionella biofilm might promote substantial Legionella growth and dissemination in weeks or months. In contrast, a building with an efficiently designed potable water system that maintains high disinfectant residuals, elevated hot water temperatures, regular water flow, and has no preexisting Legionella population may not support Legionella colonization at all.

2 For example, a building that is damp and has poor ventilation in a humid region might develop mold growth in a few days that will proliferate unless these conditions change. In contrast, a building that is dry and well-ventilated in a arid climate might not develop significant mold growth for weeks, months, or at all.

3 For example, a building potable water system with a lead service line, lead-soldered plumbing fittings, elevated water temperature, and low mineral content would create conditions conducive for lead to leach into the water in a few hours. In contrast, a building water system constructed with lead-free plumbing materials and supplied with water that contains corrosion control chemicals would prevent metals from leaching into the water system and reduce or eliminate exposure.