In an ideal world this would be such an easy question to answer, why?
- Every property in the UK should have a legionella sample testing and risk assessment on its water services. This report highlights the risks and puts forward recommendations to control them.
- A second document is also required, a Written Scheme of Control.
- The Written Scheme of Control sets out the tasks which are required to manage the risks.
- If legionella sampling is required, the locations and testing frequencies will be clearly documented so they can be part of the overall building maintenance programme.
Unfortunately, it is not uncommon for these documents to be missing, mislaid or completely out of date. If that’s the case, start the process to get a specialist company to provide these reports.
In the meantime, AquaCert can provide an example and general guidance on where to take samples.
EXAMPLE
Large Care Home
Legionella bacteria need to get into our lungs to cause the illness (Legionnaires’ Disease). Aerosols containing the bacteria are the principal route for an infection.
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What are the typical risk systems? |
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Risk Systems for Aerosol Generation |
Risk Systems for Water Temperatures |
Higher Risk Locations |
| Infections arise when aerosols are more dense, more prolonged and people are exposed for longer periods. | Water temperatures between 20-45°C allow legionella to grow. The bacteria grow fastest at around 37°C | Legionella prefer stagnant water conditions. Distant hot/cold water outlets may have lost or gained temperature during distribution. |
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Now you can turn this information into a sampling protocol
| First |
Hot Water Source |
What Outlets to Sample |
What it means if NO legionella are found |
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| This is the unit which produces your hot water.
It will usually be a calorifier, hot water cylinder, combination boiler or water heater. |
The best places are drain valves or a sampling point on the flow pipework just above the stored water.
If there is no sampling point, the nearest DIRECT fed outlet can be used. |
Your hot water production is clear at the time of sampling.
NOTE There could still be legionella in the distribution pipework or taps (or both). |
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| Second |
Distribution System |
What Outlets to Sample |
What it means if NO legionella are found |
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| The pipework which carries the hot water around the building. | Only check direct fed outlets during legionella sample testing, which means outlets that are not showers or fed by TMVs or thermostatic taps.
The outlets should encompass those nearest and furthest from the hot water source. Examples would normally include Kitchen taps or Sluice sinks. |
It’s unlikely there are any living legionella bacteria from the source of your hot water (calorifier, water heater etc) through your distribution pipework up to the point of entry into Shower mixers, TMVs or thermostatic taps.
NOTE It is possible that there may be legionella bacteria living downstream from TMVs, Thermostatic taps or Showers mixers. |
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| Third |
Outlets |
What Outlets to Sample |
What it means if NO legionella are found |
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| Final outlets | Outlets in empty rooms
Showers Whirlpool Baths Rarely used outlets |
If the legionella sample testing process yields a negative result, it indicates that your maintenance regime for cleaning showers or for flushing rarely used outlets is managing the legionella risk. | ||