I was thinkin of instead of using a chiller, just dig deep enough and put pipes, hook it up to a pump, pump it through the ground and into the tank. I was thinking of doing this to the coldwater tank(about 50-60 gallons). My dad was actually the one who thought of this. So, instead of using a chiller, use the ground. So, how exactly deep does it have to be so it can cool down water to 55F? We have pipes underground for our sinks, showers, ect and I check the temp of the water and it was 64F. The pipes are only like 1.5 ft deep.