Quacker/ Deaner
I also have an open loop geothermal system that is 11 years old and I have not had any problems. I have very hard water an I have never even needed to clean the coils. The brand I have is Waterfurnace - they have a good website if you need more info.
I discharge about 6 gpm when the unit is running. I use to splash it into the pond, but it would freeze up during the winter, so I expended the PVC discharge pipe under my dock, to a 7' depth and put a venturi aspirator on it. I only get about 1 sfcm of air bubbles - but thats better than nothing. I keep caged bass next to the discharge and have never had problems - no bass have died in the cage.
There are a few other geothermal threads if you do a search.
