From another thread but I think it's worthy of its own discussion:
That must be really frustrating as well though. Because i could be completely wrong with this but legionella is based on water being stagnate and warm/hot.
If your warming water via a gas heater or a diesel heater then that doesnt apply. If like me water is being heated over night in a static van then again its not static for long enough for it to grow and certainly not whilst in transit all day.
Sometimes H&S really frustrates me. But i suppose better to be save than sorry
One of our franchisees is going to hot using an immersion shortly so this is on my mind.
A general comment is that if you have water you have legionella. If you have warm water you have breeding legionella. No-one anywhere seems happy to give any kind of numbers, volumes or the time it takes to become a serious problem. So, does a hose full of warm water that's then left in the sun-warmed van for a week when you're off work in summer become riddled? Hard to say but definitely a potential risk when you consider that hotel shower heads have been a problem in the past.
Legionella is dangerous when the water is in aerosol form. That spray of mist when you take the brush off a window is a perfect example of aerosol water and if it contains legionella, it can be breathed in by someone 600 feet away and they can become infected.
There are a couple of solutions. Take the water above 60C and you kill off the bacteria. It'd be wasted heat to some extent (do you want to clean with water that hot?) and you'd have to run it through your hoses for some time while maintaining that temperature.
The better alternative would be to rechlorinate the water after the RO. You need to get to 0.5ppm if you're doing it all the time but you can raise the amount of chlorine higher for shorter periods of time to do the same job. 0.5 - 1ppm is in the same range as tap water so isn't going to harm customers' windows. That's what we're looking at. Dose the IBC every fill and it should all be just dandy. The amount and manner of dose is TBC.
The problem is that all the literature online is very vague on the detail and no-one's done a full analysis for our industry. However, I do feel it's an accident waiting to happen.
Vin