Section - Potable Water Systems

Cold Water Systems.


Emergency disinfection of the cold water potable water system shall be achieved by the following halogenation procedure:

  • building occupants and facility personnel shall be informed that halogen disinfection with concentrations exceeding EPA allowable limits for drinking water will be used in the procedure 
  • an EPA-registered and labeled drinking water product shall be added to the hot water system in accordance with use directions for the EPA-labeled product 
  • all outlets shall be flushed until halogen concentration at representative distal taps and faucets is confirmed by measurement and documented 
  • close all outlets and disinfect with halogen for a minimum of 2 hours (not to exceed 24 hours) 
  • thoroughly flush all outlets. Measure halogen concentration at representative outlets to confirm it is within EPA limits before reuse of the system. Example: One EPA approved halogen is chlorine. If using chlorine for disinfection, the level of free residual chlorine should be raised to 20-50 mg/L (ppm) of free residual oxidant, as chlorine and maintained at approximately 50 mg/L (ppm) for one hour or at approximately 20 mg/L (ppm) for two hours. The pH of the water should be maintained below pH 8.0 to prevent significant reduction of disinfection efficacy. (Note: If chlorine dioxide is used, pH control is not required)
  1. cleaning, disinfection and/or replacement of system components
  2. flushing or mixing of stagnant or low flow areas
  3. other treatments and any required monitoring that the Legionella water management plan team decides are necessary for
8.2.4 Water Treatment.


The Legionella water management plan shall include a written water treatment plan for control of microbiological activity, scale and corrosion. The water treatment plan shall:

  • specify all equipment and chemicals used for the purpose of treating the open recirculating loop 
  • require that control of solids in cooling tower water and in basins be achieved through filtration, physical cleaning, or other means such as chemical water treatment Note: Contaminants in a cooling tower system, both suspended and precipitated solids, facilitate the growth of bacteria and biofilms that can increase the potential for Legionella. 
  • include a schedule for required inspection, maintenance, monitoring and a corrective actions log 
  • identify the persons responsible for providing and maintaining the system water treatment 
System Maintenance.


The Legionella water management plan shall include: 

  • inspection frequencies for water containing vessels and system components 
  • maintenance procedures based on equipment manufacturers’ recommendations for ​
Emergency Disinfection. 


The Legionella water management plan shall include procedures to be followed if there are suspected Legionellosis health problems associated with the use of potable water in a building system. The plan shall include any directions given by state and local health department authorities. When an outbreak of Legionellosis has been associated with a potable water system or suspected cases of the disease occur, disinfection shall be performed. These procedures shall include criteria for when and where to test for Legionella in the potable water. The method of emergency disinfection shall be thermal or chemical or any combination. Point-of-use filtration (0.2 micrometer) may be used for Legionella control at specific taps and faucets.
Note: Emergency disinfection of hot and cold water systems is potentially hazardous and can cause increased corrosion rates in the potable water system. Routinely performing these procedures can significantly impact equipment/piping lifecycles and is therefore not recommended.
Note: Combining heat and flush disinfection method and chemical disinfection method is the most effective method of emergency disinfection.
Note: After emergency disinfection, re-colonization is likely to occur unless proper temperatures are maintained or a continuous disinfectant residual is maintained or other design/maintenance conditions that caused the problem are corrected.
Note: Point-of-Use filtration does not disinfect a system. It provides hazard control at the point of use only.

Water Treatment.


The Legionella water management plan shall include the: 
•  monitoring method and frequency of temperature measurement in the hot and cold water systems. Note: Water temperature recommendations for Legionella control are as follows: hot water heater outlet temperature at or above 60°C (140°F); hot water temperature at coldest point in hot water heater, storage tank or distribution system at or above 51°C (124°F); cold water temperature in any part of system at or below 25°C (77°F). If the Legionella water managementteam determines that these temperatures cannot be achieved, then it may find that additional hazard control measures are required. 

  • monitoring method and frequency of chlorine residual measurement in the hot and cold water system. Note: The chlorine concentration recommendation for Legionella control is >0.5 ppm (mg/l) free residual oxidant, as chlorine. If the Legionella water management team finds that this recommended concentration is not achieved, then it may determine that supplemental treatments are required. 
  • inspection and maintenance schedule for all water treatment equipment and chemicals, which shall be EPA-registered and labeled for potable water disinfection; all treatments shall be applied in compliance with local, state and federal regulations 
  • schedule for any monitoring required as part of the water treatment plan 
  • procedures following water supply interruptions or breaks in water supply piping 
  • identification of responsible persons for maintaining equipment and chemicals
Heat and Flush Disinfection


An effective method for emergency disinfection of contaminated hot water systems is thermal shock treatment to be implemented using the following procedure:

  • local building and sanitary codes shall be used to set temperature limits 
  • building occupants and facility personnel shall be informed that disinfection with water temperatures that could cause scalding will be used 
  • water temperatures shall be maintained at 71-77°C (160-170°F) while progressively flushing each outlet in the system 
  • a flush time of thirty minutes shall be attempted. The intent is to provide thermal eradication for as long as possible up to thirty minutes; the outlet flow rate shall not surpass the capacity of water heaters to maintain temperature. Note: In healthcare facilities, flushing should be performed in a manner that reduces the risk of scalding and aerosolization of potable water in patient-care areas. This can be accomplished by flushing to waste upstream of outlets, by flushing risers and recirculation loops from outlets not used by or near patients, or by flushing outlets in patient rooms at low flow or with aerators removed.
Chemical Disinfection Method


An effective method for emergency disinfection of contaminated hot water systems is shock halogenation to be implemented using the following procedure:

  • building occupants and facility personnel shall be informed that halogen disinfection with concentrations exceeding EPA allowable limits for drinking water will be used 
  • an EPA-registered and labeled drinking water product shall be added in accordance with use directions for the EPA-labeled product 
  • all outlets shall be flushed until halogen concentration at representative distal taps and faucets is confirmed by measurement and documented 
  • close all outlets and disinfect with halogen for a minimum of 2 hours (not to exceed 24 hours). 
  • thoroughly flush all outlets. Measure halogen concentration at representative outlets to confirm it is within EPA limits before reuse of the system. Example: One EPA approved halogen is chlorine. If using chlorine for disinfection, the level of free residual chlorine should be raised to 20-50 mg/L (ppm) of free residual oxidant, as chlorine and maintained at approximately 50 mg/L (ppm) for one hour or at approximately 20 mg/L (ppm) for two hours. The pH of the water should be maintained below pH 8.0 to prevent significant reduction of disinfection efficacy. (Note: If chlorine dioxide is used, pH control is not required) 
  • hot and cold storage tanks
  • ice machines
  • water hammer arrestors
  • expansion tanks
  • water filters
8.2.2 New System Startup. 


The Legionella water management plan shall include a written startup plan that includes:

  • any cleaning steps that are part of commissioning of the cooling system, with responsible persons identified 
  • a means of ensuring that an ongoing water treatment program is initiated immediately once the system is charged with water. 

Section - Cooling Towers and Evaporative Condensers


This section describes requirements for cooling towers and evaporative condensers. 
Note: In addition, recommendations and guidance on the design, maintenance, and operation of cooling towers and evaporative condensers are provided in ASHRAE Guideline 12 and in the chapter on water treatment in the ASHRAE Handbook—Applications (see Bibliography in Appendix A).
Note: Other resources include Association of Water Technologies (AWT) and the Cooling Technology Institute (CTI). See Appendix A, Bibliography.

Ron George CPD, President, Plumb Tech LLC


With 35 years of experience designing plumbing and mechanical systems for several major architectural, engineering, and design & construct firms. He has designed plumbing, mechanical, and fire protection systems for all building types including airports, stadiums, industrial manufacturing facilities, office buildings, commercial and retail buildings, hospitals, laboratories, prisons, jails, hotels, apartment buildings, military projects, high rise and educational facilities.

8.2.6 Disinfection of Cooling Towers and Evaporative Condensers.


The Legionella water management plan plan shall include written disinfection procedures for:

  • remedial on-line disinfection which includes the conditions that would prompt its application and identifies the persons responsible for initiating and executing the procedure 
  • emergency disinfection which includes the conditions that would prompt its application and identifies the persons responsible for initiating and executing the procedure.
  • shower heads and hoses
  • electronic faucets
  • aerator and/or faucet flow restrictors
  • non-steam, aerosol generating humidifiers
  • water heaters with any stored volume of wate
Hot Water Systems.


Disinfection shall be accomplished by the methods of Section 8.1.5.1.1 and/or 8.1.5.1.2.

Equipment Siting. 


At the time of cooling tower installation (either in a new system or as a replacement in an existing system), drawings shall be reviewed and siting issues addressed prior to beginning construction. The Legionella water management plan shall identify and address potential hazards related to any:

  • equipment siting issues that allow contamination from building systems or facility processes to be drawn into the equipment 
  • equipment siting issues that allow cooling tower or evaporative condenser exhaust to infiltrate buildings 
  • equipment access issues that inhibit maintenance and inspection activities. 
8.2.3 System Maintenance.


The Legionella water management plan shall include a written maintenance program that:

  • specifies the frequency of inspections for general system cleanliness, drift eliminator condition, condition of fill material, and water distribution system operation 
  • includes basin or remote sump cleaning and purging of stagnant or low flow zones 
  • identifies responsible persons and includes a mechanism for recording maintenance activities and inspection notes. 
New Construction/Renovation. 


For new construction or for significant modifications to a potable water system, drawings shall be reviewed to identify and address issues prior to beginning construction. The Legionella water management plan shall address potential hazards from: 

  • possible cross connections between potable and non-potable water 
  • inadequate access to equipment with water storage capacity such as water expansion tanks, water hammer arrestors and water heaters 
  • dead legs or low flow portions of the piping system 
  • stratification in hot or cold water storage tanks and heaters 
  • heat transfer from hot or cold water piping or heat rejection equipment resulting in heat gain in cold water piping or heat loss in hot water piping

Water Treatment, Sanitizing, Flow Diagrams, Legionella Water Management Plans

New Systems, Startup and Shutdown.


The Legionella water management plan shall include procedures for: 

  • cleaning and disinfection before commissioning any new system 
  • shutdown, including any draining, purging, cleaning treatment and control settings 
  • any unplanned loss of operating energy, loss of water treatment chemicals or system component repair or replacement 
  • restarting safely from a drained shutdown condition or from an undrained (stagnant) shutdown condition 
  • monitoring and treatments following water supply interruptions or breaks in water supply piping 
  • the method and frequency of temperature measurements in the water heater and in the distribution system Identification of the responsible persons for these activities shall be documented.
8.2.5 Shutdown and Startup.


The Legionella water management plan shall meet the following requirements regarding startup and shutdown procedures. The Legionella water management plan shall include written procedures for:

  • shutdown that includes all chemical pretreatment steps or pump cycling protocols, as well as provision for system drainage for shutdown periods of longer duration, as specified in the plan 
  • startup from a drained system 
  • startup from an undrained (stagnant) system that exceeds the number of idle days specified in the plan. Each of these shutdown and startup procedures shall identify the persons responsible for initiating and executing the procedure.
  • inspection notes and a corrective actions log 
  • regular updates of system component operating manuals 
  • identification of the responsible persons.

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