Dealing with positive test results

Even though immediate shut down is not always essential, there is never going to be much time for delay once you have a Legionella positive result from a routine sample from an Independent UKAS (United Kingdom Accreditation Service) testing laboratory.

Eliminating the sources of infection and avoiding a major incident will typically involve several stages:

Risk assessment to identify where the danger lies (dead legs, redundant piping etc). Having an up to date risk assessment in place will save time.

Initial disinfection to control the outbreak (but often not remove the root cause).

Remedial work to remove major risks and the cause of the current positive test results.

Further disinfection and on-going sampling because remedial work such as the removal of system dead legs is very likely to disturb bacterial colonies and cause them to be distributed around the piping circuits.

While newer buildings may have the advantage of zoned water systems and built-in flushing valves, older buildings are often a mystery even to the people who manage them. There will probably be a history of refurbishments and minor works such that no-one really knows the system, or could locate every pipe, outlet and potential risk area.

Having a good, current and legally compliant risk assessment in place would mean that all this investigative trace-and-access work is to hand, rather than something which now has to be done urgently and, in all probability, expensively.