Are there any known cases of legionella affecting users of hot tubes? As far as I am aware it lurks in pipework/plumbing, in and around bends where the flow is stopped and waiting for the right opportunity to spring its harmful affects by exiting through shower heads where it is carried in water droplets and inhaled into the lungs of the unsuspecting victim. Another cause is through air con but can spa pools spread the disease?

Yes. Loads. Including the very recent Stoke on Trent outbreak (although arguably those affected were not technically users). Check out the HPA/HSE guidance document on the matter.... http://www.hpa.org.uk/we...d/HPAweb_C/1200471665170 Its currently under review following the L8/HSG274 update but should cover what you need to know. The key issue in spa pools is the proximity of the respiratory zone of the user to the surface of the bubbling water. As an aside...air con doesn't have any direct involvement with legionella. Cooling towers (which DO have direct involvement!) can serve chillers which in turn serves air conditioning plant but the water in those towers should have very little to do with air being blown into a building.

Spa Pools are at risk; if only the Water Boards had a responsibility to eradicate all Legionella present in their system in the first place.

Indeed - particularly in spa pools which just end up full of dirty dirty people. Quite naive actually to expect to have zero microbiology in a water system as some dutyholders/contractors seem to aim for. A bit like expecting zero accidents.

Wow that's it then. Water temp is 40 degrees C and Bromine instead of chlorine tablets used, apparantly better at the higher temps. Filtration is at top water level so anything at the top gets filtered out. I have been told that three monthly water changes are sufficient. What is the issue with proximity of breathing zone, how much distance do we need? Water level is usually chest high. Interesting this.

Three monthly water change? Sounds dodgy to me - I refer you to the above guidance for details. BUT Risk assessment is the key to all as ever and there is not necessarily ever a one size fits all solution. Don't even know if you're talking about a domestic hot tub or a commercial spa pool - guessing the former? In which case three months MIGHT be fine. I wouldn't stress the breathing zone bit too much...it's part of the risk but not one you can really control - otherwise you'd never get in the pool! Just aim to prevent the growth and proliferation of legionella (and other water bugs too such as pseudomonas).

The breathing zone is a significant consideration of the overall risk factor, when considering use of spas etc. The 'issue' is that spas produce respirable droplets and the very nature of how you use a spa i.e. you sit and/or lie down in it, means that the respirable droplets are within your breathing zone and that it itself creates a significant risk of infection if L is present in the water. If the droplets weren't within your breathing zone then the risk would be significantly lower, but the way that spas are used make this essentially unavoidable (unless you chose to stand up all the time). In very simple terms, the are a number of key factors to consider when considering the risk associated with L. 1. Are the conditions present for the proliferation of L? 2. Are respirable droplets likely to be produced? 3. Are these respirable droplets likely to enter the breathing zone? 4. Will vulnerable groups be exposed? If the answer to any of these is 'no', then the risk reduces (by varying degrees). However, with regard to spas the answer to questions 2 & 3 are 'yes', and therefore this makes it particularly important to make sure that the answer to 1 is 'no', and the way to do that is to ensure adequate microbiological control. If it helps, while I assumed that the original question was in relation to a commercial spa, it appears that the question relates to a home spa. I have been using one for about 5 years, which has a significantly lower bather load than a commercial spa. I carry out regular testing with dips strips, and have been dosing with chlorine, regular filter changes and have so far managed to survive to tell the tale. The breathing zone IS an issue but an unavoidable one, as such is the nature of using a spa. If you keep 'control' then you shouldn't have a lot to worry about. Hope that makes more sense.

How does this discount warehouse have a hot tub used by members of the public?

All good advice but also need to remember that there is a particular "risk profile" and as HSE state: "However, some people are at higher risk, including: people over 45 years of age smokers and heavy drinkers people suffering from chronic respiratory or kidney disease anyone with an impaired immune system" So, a fit and healthy "safety bod", a non-smoker etc should be at very low risk! But remember that men are more prone to contract the disease than women! Phil

I think you probably hit the nail on the head there, or at least inadequately treated. Legionella is a major concern in my industry with the cooling towers, water usage and warm environments present, and as you rightly say if correctly managed there should never be a problem. It's when people or companies step outside of their skillset with something that could be regarded as quite innocuous, such as a tub of water (what could be harmful about that?) where control is lost. Don't let the legionella talk put you off your hot tub though, you are aware of the dangers therefore are already armed with the knowledge of properly controlling the water, so apply that and you won't go wrong :) As for legionella being eradicated via the water companies, I think that would be a problem seeing as legionella quite happily thrives in soil (foot to hot-tub transfer?). Alan