Privacy Settings Where do Hotels use Legionella Test Kits? - Aquacert
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Where do Hotels use Legionella Test Kits?  This is a common question we get asked.

Where to Check for Legionella

Since hotels receive numerous guests on a daily basis, such establishments have several water sources, systems and features. When a hotel gets a positive result, their first concern is whether the problem is local (to a single room or tap) or if the bacteria are endemic (everywhere). This is where a sampling plan is required, each hotel will be slightly different but the basic thought process is the same.

1. The main distribution system

Hot Water Source – Does your calorifier/water heater have legionella?

Test the stored hot water first, if there is a problem here – you will have a problem everywhere.

Sentinel Outlets

Next test is the furthest hot water outlets. This could be top & bottom floors for a multi storey hotel. Maybe it is the four corners of a large single storey hotel. In any event the locations should either be fed direct or taken just before any TMV valves.  If these results come back clear, you know that your main distribution system has no legionella.  If also means that any other samples which are found to contain legionella will probably be due to a local issue.

2. Other outlets


Legionella bacteria favour shower heads and hoses. This is because most shower systems sustain temperatures between 35° C and 45° C. Showerheads are also prone to scale, sludge and rust build-up, which provide nutrients to encourage proliferation.  Showers also produce vast aerosols which allow the legionella to enter our lungs as we breathe in.  Testing a couple of showers on a rotational basis will determine if your cleaning/disinfection regime is satisfactory.

Rarely used rooms or outlets

Very few hotels maintain 100% occupancy levels so some rooms will not be filled. Are there are some rooms which are typically the last to be let? Maybe the reason is due the view, noise or they are awaiting refurbishment. In any event you should be flushing all these outlets at least weekly. Why? Because legionella bacteria favour static water so pipes that are stagnating are ideal places for them to thrive. Checking one or more “not in use” rooms will determine if the flushing regime is satisfactory.


It is good practice to fit thermostatic mixer valves (TMVs) just prior to the hot water outlets in guests’ rooms. This reduces the risk of scalding but increases the likelihood of legionella bacteria being present.  TMVs lower the water temperature to a pleasant ~41°C which is pretty much the most perfect temperature for legionella to thrive. It only takes a small slip in the hot water temperatures to enable legionella to survive/pass through the hot water storage vessel.  Once the legionella get into a TMV they can remain there for years.  Even when the hot water distribution temperatures are 65°C, the TMV protects them by keeping the water at around 40°C. So if you find a [TMV fed] tap positive it is either a local problem or indicative or a past issue with the distribution temperatures. It requires a chemical disinfection to kill them.

Water storage tanks

Virtually every single hotel has one or more water storage tanks. They are crucial for ensuring all areas and rooms in the hotel have water for all workers and guests to use. If the water temperature in a cold water storage tank rises above 20°C, legionella can grow.   If you regularly monitor the temperature and it’s always below 20°C, then the location is a low risk and has no great need to be tested regularly.

3. Other Water Systems

Water features

Fountains and other types of water features are popular, everybody has an affinity to water. Unfortunately they are linked with a high risk of Legionella because of their design. Since they spray water, the aerosol they produce is a key way in which Legionella is transmitted.  Indoor water features have ambient temperatures which is higher allowing the bacteria to grow.  These systems must be treated with a UV or biocide to prevent bacteria growth, then checked with a legionella test kit to prove the preventative measures are satisfactory. A positive legionella result means anyone walking past the feature could become infected.

Lawn/plant irrigation

If your hotel has a front/back yard or gardens, chances are you have an irrigation system. Just like fountains, they spray out contaminated water droplets which people can accidentally inhale. In general, there is a higher risk of Legionella being present in these droplets since the sprinkler system is outside where temperatures are high enough for the bacteria to grow.


Author: Duncan Hollis