[Don W]

I’m speaking as an operating engineer that worked large cooling and heating systems for over 30 years. I attended numerous courses on the prevention and mitigation of these and other biological, chemical treatment, and contaminant problems.

Yes, the heat transfer fluid does not normally enter the domestic water system, but it’s the hot water temperature that poses the risk.

Water can have legionella and not affect people if the concentration is low enough, but keeping your hot water below 140* is dancing with the devil.

I keep my DHWT at 160*f. Yes, that’s a bit hot and perhaps a bit wasteful, but that’s my preference.

[Tell It Right]

Thanks for the tip on the water temp.