That could be a problem..
https://en.wikipedia.org/wiki/Legion...onella_control
However, if the temperature is below freezing, your outdoor
or attic Collector array can be frozen. That can cause damage and leaking. So, you need to use one of the standard methods to prevent that damage.
Use a drain-down system with a smart controller, or use a closed loop system, that uses water with non-toxic antifreeze as a transfer medium between collectors and the indoor (Double-Wall) heat exchanger that heats your storage tank.
The HX must be double wall to prevent any antifreeze contaminating the
potable hot water.