Legionella testing

There is a perception that people have to take water samples and check for legionella bacteria. This is NOT the case. Microbiological monitoring is a method of monitoring the levels of microbiological activity in a sample of water. Routine monitoring is NOT necessary (see ACOP L8 pg46-47 paragraph 183-187) because it is known that legionella bacteria are found in mains water.

Experience shows that legionella bacteria are present in about 13% of water samples i.e. 1 in 7 but this is NOT a control measure. It is known that legionella (and other bacteria) occur in perfectly fit to drink mains supplied water. So spending time and money on samples is missing the point. The key is to implement adequate control measures and a written scheme for reducing the risk.

Risk assessment and reduction

Archer + Stone can arrange for samples to be taken where it is deemed appropriate e.g. where low temperatures (in hot water systems) are set due to using biocides or in ‘at risk’ hospital wards OR where the client requests or specifies that is what they want. Our approach is to help you comply with the law, reduce the risks from legionella and do so cost effectively. So we’ll advise you where to save your money and legionella testing is one such area. As a comparison a farmer would feed a pig to fatten up for market. He wouldn’t simply keep weighing it because measuring doesn’t achieve the aim. His objective is to sell it which is dependent on its weight so his effort should be directed to feeding it. Similarly taking water samples to measure for legionella is only a measure. The primary aim is to minimise the risk so it is more important to assess the risk and put in controls to reduce the risk.

(You wouldn’t swab your hands to measure bacteria and pour over the results deciding how to proceed. To avoid stomach bugs you probably wash your hands before eating, after going to the toilet or gardening etc. You know there are bacteria on your hands and you constantly use effective control measures i.e. thorough hand washing!)