How to Overcome the Most Common Issues Identified During Legionella Bacteria Risk Assessment Walkthroughs 

Implementing effective Legionella bacteria mitigation programs can be a daunting task. From ensuring the appropriate facility departments are involved, to selecting optimal domestic water temperatures, it may seem difficult to know where to begin.

Below are the five most common issues identified during Legionella bacteria risk assessment walkthroughs and how to overcome them.

1.Drinking water is heated to temperatures that promote bacterial growth

The number one issue most commonly identified during risk assessment walkthroughs is the hot drinking water is not heated to high enough temperatures to kill Legionella bacteria. As we mentioned in a recent post, Legionella bacteria proliferate exponentially at water temperatures between 77-120°F. However, many facilities heat their hot water anywhere between 105°F-120°F to comply with healthcare scalding restrictions. One way to satisfy temperature restrictions while also combating Legionella bacteria growth is to install thermostatic mixing valves. This will allow your facility to heat hot drinking water to temperatures that will rapidly kill Legionella bacteria (140°F-160°F) and then temper the water down to safer temperatures at faucets and showerheads.1,2

In the same vein, it is important that water stored in hot water storage tanks is maintained at temperatures above 140°F.OSHA states that water heaters maintained below 140°F may foster Legionella bacteria growth.Similarly, ASHRAE Guideline 12-2000: Minimizing the Risk of Legionellosis Associated with Building Water Systems recommends that, where practical in health care facilities, nursing homes, and other high-risk situations, hot water should be stored above 140°F.New York State Department of Health (NYSDOH) recommends hot water be stored above 140°F when a facility has the necessary mixing valves or anti-scald valves to reduce the final water temperature to that required by local codes.4

Cannot meet these elevated temperatures in the hot water system due to energy or scalding concerns?
It may be wise to consider supplemental treatment in the drinking water system.

2.Regularly Clean and Disinfect Water Tanks

Water storage tanks often are ignored, but regularly cleaning and disinfecting potable water storage tanks can help minimize the growth and amplification of Legionella bacteria. If tanks are not cleaned regularly, sediment can build up on the bottom. A study by Qin et. al. found a positive association between opportunistic pathogens (including Legionella pneumophilia) and nutrients found in water storage tank sediment.5

The Association of Water Technologies (AWT) states that Legionella bacteria can grow in many parts of building water systems including hot- and cold-water storage tanks, water heaters, and expansion tanks. The organization recommends flushing and cleaning hot water tanks as part as an overall risk assessment and management plan of the entire building water systems.6

\Additionally, ASHRAE Guideline 12-2000 recommends that hot or cold systems that incorporate an elevated hold tank should be inspected and cleaned annually to minimize Legionella bacteria growth.1

In New York City, all domestic water tanks must be drained and cleaned at least once per year in accordance with Chapter 6 of the NYC Plumbing Code.7

NYSDOH also recommends that hot water storage tanks be drained, cleaned and disinfected according to manufacturer’s recommendations or at least annually.4

3.Faucets and showerheads are not being flushed regularly

Outlets including faucets and showerheads can harbor Legionella bacteria in the biofilms that build up on aerators, particularly when these outlets are not being used enough.

The risk from Legionella bacteria growing in little-used outlets will be significantly reduced by increasing the flow of fresh water to these outlets. Weekly flushing of these outlets for several minutes can greatly decrease the number of Legionella bacteria discharged from the outlet. Flushing does this by preventing water stagnation and increasing the levels of disinfectant residuals at the outlet.There are many options for meeting this action item in terms of frequency of flushing, flushing time, and the department overseeing this crucial task.

4.Decorative fountains are not being properly maintained

Decorative fountains are not always considered but do harbor Legionella bacteria if they are not regularly cleaned or disinfected.

In fact, decorative fountains have been associated with Legionnaires’ disease outbreaks, particularly in hotels. To combat this risk, it is essential to properly maintain both indoor and outdoor decorative fountains. It is recommended to clean the features regularly, as well as constantly filtering the water or replacing the water every few weeks.

High risk decorative fountains, such as those located indoors and/or near immunocompromised patients, or those that generate water aerosols, should be treated with biocide. Routine visual inspections and water quality tests including disinfectant residuals, temperature and pH can help control Legionella bacteria growth.1

5.Ice machines are not being regularly cleaned and disinfected

Lastly, many facilities are not aware that ice machines can amplify and spread Legionella bacteria. Even though the bacteria are dormant in cold temperatures, they reactivate and begin to grow when the ice melts. Patients and others who chew on ice chips risk being exposed to Legionella bacteria if they aspirate on the melted water.

To minimize this risk, regularly and thoroughly clean and disinfect all ice machines within your facility per manufacturer recommendations. Manufacturers have recommendations regarding filter maintenance, and it is important to follow those, as well. To help maintain the units in between thorough cleanings, clean the external surfaces daily.9

Barclay leads the industry in Environmental Group services including risk assessment walkthroughs and Water Management Program development, as well as cleaning and disinfecting storage tanks, decorative fountains, and ice machines!

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1.ASHRAE Guideline 12-2000.Minimizing the Risk of Legionellosis Associated with Building Water Systems.Published 2000.

2.CDC.Guidelines for Environmental Infection Control in Healthcare Facilities. Updated July 2019.

3.OSHA.Control and Prevention.Legionellosis (Legionnaires’ Disease and Pontiac Fever).

4.New York State Department of Health.Environmental Health Information Related to Legionellosis in Healthcare Facilities. Published April 2019.

5.Qin K, Struewing I, Domingo JS, Lytle D, Lu J.Opportunistic pathogens and microbial communities and their associations with sediment physical parameters in drinking water storage tank sediments. Pathogens. 2017(6)54.doi: 10,3390/pathogens6040054.

6.Association of Water Technologies. Legionella 2019: A Position Statement and Guidance Document.Published February 2019.

7.New York City Plumbing Code.Chapter 6: Water Supply and Distribution. .Published 2008.

8.CIBSE.Minimizing Risk of Legionnaires’ Disease.2013.

9.Joint Commission.Standard EC.02.05.01.

Picture References: 

1. legionellaby sidknee23is licensed under CC BY-NC-ND 2.0

2. “Water Faucet”by Joshua Daniel O. is licensed under CC BY-NC-SA 2.0

3. “鳥のような噴水(The fountain like a bird)”by iyoupapa is licensed under CC BY-SA 2.0

4. “Cubes”by geatchy is licensed under CC BY-NC 2.0

5. “Arromic shower head sprays water into a ceramic washbasin”by PickComfort is licensed under CC BY 2.0

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