We installed an open loop geothermal system in our new house in August 2015. I've been sent away on assignment with work for 3 years, so we haven't spent a great deal of time in the house during that time, but am coming back to it permanently in a few months. One of the things I have noticed is that we our domestic water pressure drops significantly whenever the geothermal system kicks in (they are both supplied from the same well / pump). When we had our wells, the first one supply well provides 24GPM, and the discharge one was coming in at 36GPM. Our geothermal system required about 15GPM from memory, so the flow rates were good. I'm going to get the contractor back in (both the well and geothermal), but I like to have a rough idea of what I should be asking about when they get here. I live in a fairly rural area, and know for a fact that neither of them have a great deal of geothermal experience. System works great otherwise. Could this be simply an undersized well pump? Any other things we should be looking at? Let me know what additional information you require.