I'm skeptical of this remark 2 posts up: "we had an open system installed.(must have 21 gallons per min-ours is 31) anything slower needs a closed system." Open loop can run as little as 1.5 - 2 GPM per ton, whereas closed loops are typically designed for 3 GPM per ton. Unless you have 15-20 tons installed, 31 GPM is way too much water. I'm glad you are happy with your bills. How much total tonnage do you have?