I'm not an expert on this, but...
Been in several caves that had been used as sources of drinking water at one point in time. Most recent one was used up until the owner found a dead raccoon floating in it. Although that was several years ago, you can still see the pond liner and piping the owner used to draw from the spring.
As for warm water springs and caves, I was in a small cave this year on the UT/NV border that is a warm spring, you can swim into the cave even, although its only 30' long at the most for the air passage. It's the location for the (unofficial) Western chapter of the Randy Gandy Club.
There is a much larger cave at a higher elevation that is likely related to the warm spring activity in the area.
The reason cave water is all to often unfit for drinking is due to biological contamination (crypto is a concern) or septic and agricultural run-off. Brown trout
are not a cave adapted species!