ACoP L8 principally concerns hot and cold water services and cooling towers; however, pools and spa baths are included under Other risk systems.

In a spa bath or hot tub, the water temperature is typically greater than 34°C which, combined with the aerosol spray created by deliberate agitation, presents a foreseeable risk of exposure to Legionella. This is clearly shown by the hot tub on display at a flower show in Holland creating one of the largest outbreaks of Legionnaires' Disease, in 1999. More recently, a major DIY superstore was fined £90,000 for exposing 500,000 people to the disease from a display spa bath.

To mitigate the risk of exposing staff, customers and clients to Legionella, a safety plan needs to be put in place covering system assessment, monitoring, management and communication, and surveillance:

Action Area Reasoning
Assess hazards and risks Dead-legs, stagnant water, bio films Sweat, urine, faecal matter, all of which are nutrients for bacteria.
Identify control measures Routine cleaning Rest periods, constant circulation of water, bathers to shower, filtration and cleanliness.
Monitor control measures Routine review Inspect filters and backwash daily; inspect for cleanliness - and close facility if necessary.
Management procedures Remove dead-legs Clean or replace filters, clean pool or spa surroundings - and close facility if necessary.
Surveillance Internal and external audit, check colony counts for trends - and instigate quarterly sampling for Legionella

For detailed information on managing Legionella risk, download this presentation "Swimming pools and spa baths". The Health Protection Agency has also produced a useful, single page "Tips for spa pool owners".

Typical auto analyser installation at a swimming pool

The key components of an automatic pH/Cl2 analyser (swimming pool installation):

auto analyser bullet 1 Free chlorine readout
auto analyser bullet2 Redox reading
auto analyser bullet 3 pH readout
auto analyser bullet 4 pH and Cl2 probes