Join Date: Oct 2007
Location: Ontario, Canada
I have a softwater system at home too, but not as expansive as yours.
The salt you use is probably sodium-based, since it's the most easily accessible and cheapest salt available. It swaps the "hard" particles like calcium and magnesium for sodium particles, so that you will have softer water. I haven't had any problems with my plants so far using sodium-based salts. If you are worried about the plants then you can use potassium-based salts, which are more expensive, but more beneficial for the plants.
As for the RO system, you will have to add minerals and stuff artificially back into the water if you use it alone. I know some people use 50% RO/DI and 50% tap water, so they get minerals in the water that way.
I'm not sure what you mean by short/long term exposure.
If you're worried abou the external tap water being too cold, just pump it into a large holding tank indoors, leave it overnight so that the water temperature will level with the indoor temparature, and use it then.