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Plumbing Systems and Water Quality Guidance

The Illinois Department of Public Health (IDPH) Plumbing and Water Quality Program has issued this memorandum to building owners and operators, and public water supply operators to provide guidance for maintaining water quality and safety in building water systems and in potable water distribution systems during periods of reduced use and considerations for returning building water systems to regular use.

The program recognizes many buildings throughout the state  have experienced extended periods of reduced use due to measures implemented to help slow the spread of COVID-19. This lack of use will increase water age and stagnation in water distribution systems and other building water systems. Increased water age degrades water quality by corroding pipes and plumbing materials, accumulating sediment in water systems, and reducing disinfectant levels. This contributes to the growth and spread of opportunistic waterborne pathogens (e.g., Legionella, Pseudomonas, Acinetobacter, nontuberculous mycobacteria, and fungi), increases concentrations of metals like iron, lead, and copper, and can create unpleasant tastes, colors, and odors.

Many businesses and buildings are currently taking steps to reopen, following the release of Gov. JB Pritzker’s plan to “Restore Illinois, which may be viewed along with relevant indicators at Building owners and operators and water system operators are encouraged to consider the general guidance and recommended actions noted in this document to reduce plumbing and water quality concerns.

General Guidance for Water Quality and Safety in Plumbing Systems

The best strategy for reducing potential plumbing and water quality issues is to take proactive, preventative measures to maintain water quality. IDPH and the Centers for Disease Control and Prevention (CDC) recommend building owners develop and implement water management programs. Water management programs identify hazardous conditions and take steps to minimize the growth and spread of Legionella and other waterborne pathogens. Developing a water management program is a multi-step process. For response to COVID-19, IDPH recommends prioritizing the following actions:

  • Identifying and describing the building water system(s) in and around the building or premises.
  • Identifying areas where Legionella could grow and spread or where other water quality concerns like lead contamination could exist.
  • Decide what actions can be taken in the building water system(s) to prevent water quality issues.

If your building is a significant user on a public water supply system, you should notify your water provider immediately whenever your building will experience a significant change in water demand for an extended period of time.. This allows the public water supply system to make any necessary adjustments to treatment and distribution to maintain water quality.

Following periods of lack of use, it is common for building water systems and drain waste and vent (DWV) systems to experience leaks, blockages, and other mechanical issues, such as air-locking, water hammer, and malfunctioning valves and fixtures as a result of corrosion, sediment accumulation, and entrapped air. To reduce these concerns, valves should be opened and closed slowly and turned on systematically (see Attachment A). Additionally, the fluid maintaining trap seals on DWV systems may have evaporated over time. These traps are intended to prevent sewer gases and vapors within the DWV system from entering the building. Therefore, all traps should be filled by slowly pouring water into all fixtures (sinks, tubs, showers, floor drains, etc.), until the trap seals have been properly restored.

The program recommends consulting with a licensed plumber prior to returning systems to use, as it may become necessary to repair leaks, clear blockages, and repair or replace malfunctioning plumbing fixtures, fittings, and appurtenances. Plumbing must be performed by plumbers licensed and registered in accordance with the Illinois Plumbing License Law (225 ILCS 320/) and installed in accordance with the Illinois Plumbing Code, Title 77 Ill. Adm. Code Part 890.

After building owners and operators have followed recommended actions for start-up (see Attachment B), IDPH recommends facilities maintain water quality by adhering to a comprehensive water management program that includes regular monitoring of water quality parameters, such as temperatures, pH, and disinfectant levels.

Shock Disinfection of Plumbing Systems

Prior to reoccupying buildings that have been vacant for an extended period, building owners and operators may consider performing a shock disinfection of the building water system(s). Shock disinfection refers to introducing high concentrations of disinfectant or high temperature for a relatively short period of time. Before disinfecting building water system(s), facilities considering disinfectants for shock disinfection should ensure appropriate measures to protect the public water supply are in place and communicate their proposed actions to the appropriate authorities. Operators of buildings connected to a public water supply should contact their water supplier prior to disinfecting. Operators of buildings connected to a private water supply or private sewage disposal system should contact their local health department prior to disinfecting. Appropriate measures to protect the connected water supply or water source include isolating the building’s water system(s) and verifying backflow devices are installed where required and tested by a certified cross connection control device inspector (CCCDI), as required by Title 77 Ill. Adm. Code Section 890.1130. Notification of the proposed disinfection should be given to all individuals who may be on the premises during disinfection activities. Additionally, protective measures should be put in place to ensure users are not harmed by disinfection, e.g., signage, disabling fixtures, and providing alternative sources of water.

Following disinfection, facility owners and operators should determine the water is safe for use and safe for discharge. When disinfectants are used, particularly where concentrations may exceed maximum contaminant levels, facilities should ensure water is flushed and residual disinfectant has returned to its normal concentration. Where temperatures have been increased for disinfection, facilities should ensure water temperatures at outlets are returned to a temperature safe for use.

When considering shock disinfection, facilities should be aware of possible adverse effects on the integrity of the building water systems, DWV systems, and sewage treatment systems, e.g., corrosion, pin-holing, temperatures exceeding pipe ratings, incompatible plumbing materials, and interference with sewage treatment systems. These negative effects are amplified when disinfection is performed improperly, e.g., too often, too high of temperatures, or too high of concentration of disinfectants. Direct dischargers should notify the Illinois Environmental Protection Agency’s Division of Water Pollution Control to determine if additional actions are necessary to prevent pollutants from entering waters of the state. The program recommends disinfection only be conducted by professionals with expertise in these processes and with knowledge of applicable regulations.

Buildings Primarily Serving Children, including Schools and Day Care Facilities

Lead and other heavy metals can enter drinking water when plumbing materials containing lead corrode or wear away. Some common plumbing materials that contain lead are lead service lines, brass fixtures and appurtenances, chrome-plated brass faucets, galvanized pipes, and pipes, fittings, and fixtures joined with lead solder. Lead-bearing plumbing is more likely to be found in older buildings, but especially in those constructed before 1987. The concentration of lead in water increases with the duration of time the water sits (stagnant) in plumbing systems and may vary depending on a system’s age, materials present, and water chemistry. Young children and infants are particularly vulnerable to the harmful effects of lead. Therefore, operators of water systems at schools, day cares, parks, or other facilities serving children should prioritize lead in drinking water as a possible hazard and take necessary steps to flush their plumbing system following periods of absence or lack of use. The program recommends  facilities reopening take actions to flush their systems prior to reoccupying. It should be noted that levels of lead in water can increase relatively quickly after flushing, therefore routine system flushing, flushing fixtures immediately prior to use, and utilizing point-of-use filtration when water is used for drinking and food preparation may be necessary to further reduce exposure to lead in drinking water. More information about best practices to reduce lead and water can be found in the IDPH Lead in Drinking Water Fact Sheet and in the resources below.

Schools and licensed day cares that have conducted lead in water testing to comply with regulations should review testing information and remediation plans to inform decisions when reopening.

For additional questions or concerns about lead in drinking water, contact the program at

Other Building Water Systems

Buildings can have many different types of water systems, including decorative water features, swimming facilities, HVAC systems, and cooling towers that may contribute to the growth and spread of Legionella. When reopening buildings, building owners and operators should identify and address all water systems in the building and on the premises. For these building water systems, the program recommends reviewing national standards, manufacturer’s recommendations, industry best practices, and applicable regulations. When determining appropriate measures, facilities may consider checking with one or more consultant(s) with experience and expertise in managing such systems or devices.

CDC guidance offers general recommendations for decorative water features, hot tubs/spas, and cooling towers in their Guidance for Building Water Systems.

Public Water Supply Operators

With many buildings unoccupied or operating with reduced use, public water supplies may experience issues maintaining disinfectant levels throughout the distribution system. A few examples of areas where water demand may be significantly reduced include distribution zones primarily serving school campuses, commercial, retail, bar/restaurant districts, and certain industrial areas. Through this time of reduced demand, water suppliers should monitor water use and water quality on their distribution system to focus flushing efforts (install auto-flushers or increase frequency of hydrant flushing) on distribution zones impacted by reduced use and maintain disinfectant residuals. Special attention should be given to impacted distribution areas supplying at-risk populations and buildings served by dead-end water mains.

Many preventative and responsive measures for building water quality rely on incoming water having appropriate levels of residual disinfectant and corrosion control. As buildings and businesses take steps to reopen, IDPH’s Plumbing and Water Quality Program recommends they consider the effects of prolonged stagnation on their building water systems and take appropriate actions. These recommendations include communicating with water suppliers about topics like anticipated changes in water demand, water distribution system flushing, backflow prevention at service lines to buildings, proposed disinfection of building water systems, and general questions about water quality in their area. Water suppliers are a critical participant in recommissioning building water systems safely. Where feasible, the program encourages water suppliers to support their users by:

  • Communicating. Inform users of the type of disinfectant used, inform users of the residual disinfectant levels, and note any recent disruptions or proposed changes in the water treatment supply.
  • Assisting. Work with building owners and operators to ensure standard checkpoints near the building or at the meter to the building have recently been checked and disinfectant residuals entering buildings meet expected standards.
  • Flushing. Install auto-flushing devices or increase hydrant flushing in areas experiencing reduced use.

Last Updated:  7/22/2020

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