Legionella Testing Of Domestic Water

Legionella Testing Of Domestic Water

When a customer asks whether they should test for Legionella in their domestic water, the answer is not always clear.

Every building should establish some form of a Water Management Plan for their facility. This might include monitoring disinfectant and temperature levels, which are the first and easiest ways to minimize conditions which are hospitable to pathogens.

Doing such tests may trigger the need for remedial actions. If testing reveals that control limits are not being met, what steps will be taken to bring limits back into line?

  • Are the lines being used and flushed?
  • Are temperatures and disinfectant levels compliant? If not, investigate why and take actions to bring them back in line.
  • Should temperature be boosted for hot water disinfection or should secondary disinfection be considered and employed?

Measure Water Parameters

Run the water until it gets hot. If that takes longer than a minute, this could indicate a local problem such as a mixing valve or a system wide imbalance. Record temperature, pH, and chlorine of every sample collected. Graph data as you go, the LAMPS Water Management Plans Chemtex supports will allow for easy data management. Graphical analysis can help you identify a potential problem, if one exists.

Cold Water Samples

When sampling domestic water for Legionella, most operators focus on the hot water system. Remember to periodically check the cold water at the point of entry and a point of use, you may find an issue in this system. Many buildings with low water use may detect Legionella in the cold water system due to stagnant water conditions. Routine water flushing can minimize this problem if one exists.

Proactive Legionella Testing

Some facilities proactively sample for Legionella as part of a plan to minimize risk. Even though there has been no evidence of the microbe, they engage in a proactive preventative testing program. The testing validates the supposition that there is no Legionella present. (More about Legionella testing here.)


If a facility wants to engage in proactive Legionella testing, we recommend such testing must be part of a complete Water Management Plan.

Sampling should be specific for that facility and based on a multitude of influences. One primary consideration in crafting that plan is deciding what corrective actions the facility will employ immediately if there is a positive test for Legionella. There are no acceptable levels of Legionella in domestic water.

If the team finds Legionella during routine environmental sampling (in the absence of disease), the CDC suggests exploring possible reasons for the growth. They also offer corrective actions, some simple and some more aggressive. Here are CDC guidelines for Monitoring Your Building Water.

Bottom line: If a customer wishes to test domestic water for Legionella, they must also have a plan in place to remediate the problem if one is found. If they get a positive Legionella test, a planned remedial responsive action needs to be taken immediately. The plan should outline exactly what actions will be taken and how they can be employed

Chemtex Can Help!

If you’d like to perform proactive Legionella tests in your building’s water systems, talk to us we can help you prepare your facility. Furthermore, we can help set you up with a Water Management Plan that will prepare you how and where to test as well as how to address any eventual test results. Please give us a call!

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