Legionella testing frequency is a grey area. However, regular testing is an important part of managing the risks posed by Legionella bacteria (the cause of Legionnaires Disease).
If you’ve had a risk assessment, the assessor may have made a testing frequency recommendation. Failing that, you should choose a testing frequency that suits the environment you wish to test. For example, an environment with no aerosol creating outlets (e.g. shower heads – Legionella bacteria is airborne) may be considered low risk. In that case, you may want to test annually. However, a care home, where patrons generally fall into the high-risk category, may want to test more frequently.
Whatever testing frequency you choose, it’s important to remember that the purpose of testing is to mitigate the risks posed by Legionella bacteria. The more often you test, the better.