The lady that owned my house before me was a little... off.
The water supply to the house was a "gravity fed spring system." That is, in the woods behind the house, up a hill which situated it higher than the second floor of the house, was an open pool about 10'x10', unknown depth, partialy covered with a tarp supported by 2x4's. At the bottom of the pool was a copper pipe that ran down hill to the basement, where it connected to the houses water supply pipes. The pool is full of leaves, frogs, and god knows what else. It was goddamn disgusting.
As a condition of sale, she had a new well installed. But they left the old water feed in place in the basement, just capped it with a ball valve. So that's what I use for watering the plants outside, and for feeding my immersion cooler. I just take extra care that the water is contained and doesn't leak into the wort. I don't feel too concerned about where the water goes after heating up, as its not potable, and not doing anyone any good as is.