My TDS meter also gives water temperature and even in the height of summer last year it never approached 20 degrees C. This last few days it has been around 9/10. My water comes from pipes in the ground that has been treated and is several degrees lower than the ambient temperature. But an RO in a hot shed might build up enough temperature in a short space of time.
As long as my tank is algae free and the outside temperature
averaging less than 20 deg C over several days and my water has not been used for several days - I personally would not give it a second thought.
Also - for legionnaires to grow it needs an organic agent such as algae or rust in or touching the water.
Water that collects for a long time is also at risk. So if my R/o were in a hot garage then the water stagnating in that while I was a way mid summer should be flushed through?[/color][/color]IMO there is more risk from hot tubs/whirlpool baths/showers especially abroad in hot non-european countries where the water source is less reliable.
Those at risk tend to be late middle age/elderly/smokers. (So except for Dai - we're ok!
)