Matt Freije discusses a water management plan performance study at the 2022 Emerging Water Technologies Symposium.

Data from a 2021 study showed that ASHRAE Standard 188 water management programs (WMPs) can effectively reduce Legionella in domestic (potable) plumbing systems, but a shockingly low percentage of facilities are performing WMPs well.

The study started with the assumption that reducing Legionella and other pathogens in building water systems requires procedures that effectively control growth and transmission factors such as temperature, chemistry, water age, and biofilm (“control measures”). And, for a water management program to be successful, control measures must be comprehensive, covering all appropriate measures for all water system and device types that present a risk, and the control measures must be implemented.

Out of the total number of facilities that should have a Legionella water management program per the risk factors outlined in ASHRAE 188, the percentage that have developed a comprehensive WMP is unknown and is difficult to determine based on a simple survey in part because, if asked, some facilities would report having a comprehensive WMP—probably in good conscience—when in fact they have policies rather than control measures, or control measures that are ineffective, inadequate, or non-specific. 

According to research funded by the Water Research Foundation (ASDWA 2021), the percentage of facilities with comprehensive WMPs is likely very low. Only 50% of education and hospitality facility managers surveyed had heard of ASHRAE 188. Awareness was even lower among multi-family facility managers—less than 30% knew that domestic (potable) water systems have conditions favorable to Legionella growth or had even heard of water management plans. 

Since the percentage of facilities that have comprehensive Legionella water management plans is unknown, we attempted to answer a different question, one for which we have data to study: Of the facilities that have comprehensive water management plans, what percentage are fully implementing them?

To determine the degree of WMP implementation, we reviewed the following metrics for more than 900 WMPs that had been active in HC Info’s cloud-based water management program software (“LAMPS”) for at least 12 months as of June 16, 2021:

  • Control Measure (CM) compliance (i.e., the percentage of CMs with “Okay” verification status)
  • Number of Legionella and other microbial tests
  • Number of domestic water temperature and disinfectant tests

The above metrics were compared with domestic water Legionella positivity (percentage of samples in which Legionella was found).

A detailed analysis of the findings was published in the Spring 2022 issue of the Analyst.  

Of interest was that only 19% of the 908 LAMPS water management plans that qualified for the study had control measure compliance > 80%. Fewer than 10% of the properties collected more than 20 samples for Legionella testing a year from domestic water systems. 

Two findings, outlined in the table below, were especially significant:

  • Facilities with higher control measure (CM) compliance generally performed more tests for Legionella, other microbes, temperatures, and disinfectants than did facilities with lower CM compliance. In short, facilities that kept up with their control measures also performed more tests.
  • Facilities that implemented control measures (CMs) and performed tests were likely to have lower Legionella positivity. Legionella positivity was not considered for the 0% CM compliance group because that group’s number of Legionella tests was too low to make a reliable comparison. For all other groups, the average domestic water Legionella positivity decreased with increasing CM compliance and, generally, with increasing numbers of temperature and disinfectant tests.


Table. Comparison of Control Measure (CM) Compliance with Number of Tests and Domestic Water Legionella Positivity in LAMPS WMPs Active > 12 Months

Control Measure Compliance % OK* Legionella Tests** Other Microbial Tests** Temperature Tests** Disinfectant Tests** Legionella % Positive in DW ***
0 0.81 0.14 1.44 2.98 NA
0.5-49% 5.62 2.21 8.18 12.05 24.03%
50-79% 7.21 1.54 33.99 7.95 21.40%
80-94% 17.36 7.82 26.77 32.50 16.88%
95-100% 33.16 23.67 51.53 33.84 14.98%

* As of the end of the study period, rather than the average over the life of the WMP
** Average number of tests in recent 12 months
*** For the life of the WMP, excluding sites with fewer than 6 domestic water test results total


Insights for Water Management Programs and Legionella Prevention

The data indicates that the premise of ASHRAE Standard 188 is sound— implementing comprehensive control measures can reduce domestic water Legionella positivity.

The reality, however, is that a very low percentage of facilities are fully implementing comprehensive water management plans, which is likely why reported cases of legionellosis have not decreased since ASHRAE Standard 188 was released.

State regulations and insurance requirements would increase the number of facilities with Legionella water management programs but are not likely a sole solution for reducing cases of building-related waterborne illness because enforcing full implementation of comprehensive control measures is not feasible. 

In addition to requiring Legionella water management plans, making them easier could really move the needle in prevention. Busy facilities personnel—like all of us—are more likely to do what does not take much time, effort, money, or expertise.

Automation can make water management plans easier and more effective. Automated monitoring, alerts, reporting, and documentation—and to some extent even remediation—will require less time by facility personnel and less help from outside consultants and contractors. As technologies improve, an increasing number of the key water management program elements—control measures, monitoring, and remediation—will ideally become fully automated and continuous.

Some of what’s needed is already in motion: data analytics and sharing to find relationships between pathogens and water quality parameters, water-related artificial intelligence technologies and improved sensors to automate continuous monitoring of parameters, and implementation of IoT in smart domestic water system equipment to make automatic adjustments based on parameter readings.

Technologies and software analytics are advancing so rapidly that getting to automated water management programs and the prevention of disease from building water systems may not take long. Regulations combined with automation dramatically reduced harm from fire and carbon monoxide in buildings, and it can happen with water, too.

What do you think will make water management plans easier and yet more effective in reducing the risk of Legionella and other pathogens? Please comment below.

Share This