My Building Water System Tested Positive for Legionella: Now What?

  • 23 July 2019
  • Author: Dominick Tuzzo
  • Number of views: 5387

We detected the presence of Legionella in one or more of our building water systems….. Now what do we do?

This is probably the second most commonly asked question, surpassed only by:  “Do I have to test my water systems for Legionella?”  Often the question is posed this way:

“We recently performed Legionella testing on our building water systems and found one or more positive sample results.  What should we do about it?”

The simple answer is:  “You should follow your Water Management Plan (WMP).”  The reality, however, is that quite often buildings mistakenly choose to sample for the presence of Legionella BEFORE they have even formulated a WMP containing appropriate response protocols to deal with the inevitable positive results from just such testing.

To help answer this “Now what?” question properly, we have to break down our answers to target two broad categories of water systems:  potable or non-potable systems.  Then we need to further tailor our customized responses toward either healthcare or non-healthcare settings.

Potable vs. Non-Potable Response Protocols

Potable water (i.e., domestic water) is water that people either consume or come into contact with.  It is the water we drink, bathe in, cook with, etc.  Typically, an online response protocol formulated for any potable or domestic water system must conform to the disinfectant boundaries, methodologies, and limitations set forth by the EPA Safe Drinking Water Act (SDWA).  Otherwise, you must take that particular domestic water system out of service while the remediation is in progress.

Non-potable water, however, is water that is unsuitable for human consumption (e.g., in an industrial setting) and may even be unsuitable for human contact.  Non-potable can mean:

  • utility water for boilers and cooling towers,
  • device water for decorative or ornamental fountains,
  • reclaim water,
  • raw sewage,
  • cutting water,
  • jacket water,
  • irrigation water,
  • fire protection water,
  • and more.

Response protocols for non-potable water are often system-specific.  The system can typically be taken out of service, and high-level cleanings, disinfections, and chemicals are often utilized. Process water systems in manufacturing plants, food and beverage facilities, pharmaceutical lines, etc., may offer their own unique set of limitations as to the disinfection methods to be deployed, and need to be evaluated on a case-by-case, production-line-by-production-line basis.

Finally, there are water sources such as swimming pools, hot tubs, spas, and hydrotherapy pools wherein the water is safe to come into physical contact with, but is still unfit for drinking because it doesn’t fully comply with all aspects of the EPA SDWA.  These water systems are typically taken out of service for the duration of the remediation and disinfection evolution.

Without a predetermined response protocol found within a comprehensive WMP, determining when and how to respond to positive environmental Legionella sample detections is neither simple nor straightforward.  While response protocols for non-potable systems such as cooling towers, hot tubs, and decorative fountains are usually determined quantitatively by concentration per sample (X amount of Legionella colony forming units) found within the device itself, for potable (domestic) water systems, it’s a whole new ballgame.  Positive potable water Legionella samples must be evaluated qualitatively and not quantitatively; taking into account several factors including but not limited to:

  • Trends against previous sample results
  • Recent internal or external domestic water interruptions or construction events
  • Extent of colonization via percentage of positivity’s for the number of samples obtained, and where in the building they were drawn from
  • Evaluation of suitability of sample location points, number of samples taken, and whether or not they were accurately representative and reflective of premise plumbing conditions within the building
  • Pre flush (first draw) vs. post flush sample results if taken
  • Water sample results vs. swabs if taken
  • Which species of Legionella was detected; if L.pneumophila, which serogroup
  • Domestic hot vs. domestic cold water positives
  • Temperature and/or disinfectant readings which may have impacted sample results
  • Location (near, midpoint, distal) of sample points
  • Building characteristics (e.g., size, age, complexity, recirculation, stagnation, and/or history of plumbing systems)
  • Probability of aerosolization of water from the sample point
  • Susceptibility of building occupants to water borne opportunistic pathogens

Evaluation of all these factors is necessary in determining both when and how to respond to a positive potable water sample.

Healthcare vs. Non-Healthcare Settings

The three biggest differences between healthcare (e.g., hospitals, nursing homes, assisted living facilities, etc.) and non-healthcare (commercial office building, colleges/universities, industrial/manufacturing, hotel/travel/tourism) settings are:

  1. Occupant (Host) Susceptibility to Opportunistic Waterborne Pathogens:  Healthcare routinely houses the aged and/or immunocompromised, both of whom are considered high risk groups.  Because of this occupant susceptibility, many healthcare settings have a much lower tolerance for Legionella positives found in onsite environmental water samples, and therefore, should tailor their control limits and response protocols accordingly.
  2. Clinical Surveillance:  Healthcare settings may take advantage of opportunities for clinical (patient) surveillance wherein they proactively and systematically screen patients for healthcare associated pneumonia.  This provides additional validation, correlation, or comparison of clinical vs. environmental isolate opportunities not available to non-healthcare environs.
  3. Accreditation / AHJ requirements:  Healthcare settings must follow rules and regulations established by their accrediting bodies alongside state and local departments of health guidelines and bulletins which far exceed non-healthcare requirements.

For assistance in controlling your buildings’ waterborne pathogen risks, WMPs, Sampling Plans, Risk Assessments, accredited third-party lab sampling, audits, supplemental and emergency disinfections, consultations, or any questions, contact your Chem-Aqua Water Risk Management Service Group today at:  1-866-209-3373

Written by: Dominick Tuzzo

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