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Checking for Legionella is important to both landlords and employers because of the possible health and legal consequences. Also, by conducting periodic tests, you can prevent a possible outbreak of this disease. In this article, find out why it’s necessary to make regular checks for these bacteria. You’ll also learn how and where to take the water samples.

About Legionella

These are the ones responsible for Legionnaires’ disease. Anyone who contracts it can suffer from pneumonia-like symptoms. While it can infect many people, not all are affected by this disease. Those who are vulnerable to its effects include the following:

● the elderly
● heavy smokers
● those with weak immune systems
● those with serious medical conditions such as liver disease or cancer

These bacteria are usually carried by aerosol and transmitted to your lungs. This scenario usually occurs when you’re taking a shower or bath or washing your hands.

In Legionella testing – frequency is a way to ensure the following:

● early detection of the bacteria
● health and well-being of the property tenants, employees and visitors are protected
● proper documentation of data for legal protection against possible litigation
● avoidance of any potential financial loss such as legal suits or employees getting sick
● collection of data that will support or disapprove the current risk assessment

Legionella bacteria will grow in water with a temperature of between 20°C and 50°C. Between 50°C and 60°C the bacteria will be dormant. Above 60°C the bacteria start to be killed off. It is important to keep the entire water system maintained with rarely used outlets flushed weekly, scale deposits removed from showers and taps and TMV’s serviced annually.

Where do you collect the samples?

Usually, you get samples from sentinel outlets for both hot and cold.

● For Hot Water – The first and last taps for EACH storage tank or combi boiler are the sentinel outlets.
● For Cold Water – The nearest and furthest taps from the storage tank(s) are the sentinel outlets
● Showers – It is good practice to take a sample from your shower(s)

If your furthest tap is fitted with a TMV, do not use this tap to take a hot water legionella sample as the water will be from both the hot and cold supplies – use the nearest direct fed hot tap, i.e. laundry, sluice.

How often should you conduct the tests?

For Hot Water:

There is no legal requirement to test for legionella bacteria however, your Risk Assessment will recommend the best frequency for your particular property depending on the risks highlighted in the report and the control measures you have in place. For most properties, testing every six months is sufficient if you are able to :

● Maintain the stored water temperature at over 60°C at all times
● Achieve a minimum of 50°C (55°C in Healthcare environments) at the furthest outlet of the building within 1 minute of running the tap.

If your water system is unable to achieve the above, more frequent testing is recommended.

For Cold Water:

Once again, there is no legal requirement to test for legionella bacteria however if your cold water temperature rises above 20°C there is a risk of legionella bacteria proliferating within the system (especially during the summer months). In this instance, we would advise weekly testing until the water temperature is consistently below 20°C.

If the results are all negative, this means your risk assessment plan is working.

What if the test shows positive for Legionella bacteria?

If the positive result is from the hot water system, the first action should be to pasteurise the system at 70°C for at least an hour then open all taps sequentially to draw the high temperature water through the system. Check to ensure that the water temperature can be maintained – if it starts to drop, wait for the system to re-heat to 70°C and continue flushing. Conduct a retest for legionella bacteria – if the results is still positive,

it is recommended that the water system is chemically disinfected.If the positive results are from the cold water, you will require a chemical disinfection.

Finally, if you need Legionella testing kits or just some useful advice, don’t hesitate to contact AquaCert.