Mr Willy
My Geo-Thermal system is made by Trane they have several types of systems. Here is a link to their web site
Trane Geo-thermal I have not had any problems related to anti-freeze (in texas they have to use a non toxic type). We do not have real hard winters here in central Texas (down to 15 maybe down to 10 for a day or 2) so this is not a major consideration here.
If you have real hard or corrosive water you can fill the closed loop with more friendly water (treated or city water.
I hope this helps some.
Don Stuart
