I agree that if a system is not properly designed then that would be a concern. I had similar concerns when this solutions was first proposed to me, and I spent alot of time researching it before I installed one.
The claim was made earlier that “radiant heat water wouldnt share with the potable water supply”, which would be true in many situations, but not in all situations. I was just trying to educate those who didn’t realize that there are properly designed radiant heat systems which do mix potable water with the heating system.
There are several trade-offs in each design, and this solution is no different. It’s certainly not the ‘best’ solution for all situations, but it is a recognized, valid solution which has it merits and is being installed more frequently. From my experience the system turns out to be very simple to operate and maintain and very efficient, especially when a solar heat source is being used.
If you are interested in a discussion of the benefits of one design over another feel free to contact me.