Hello everyone, nice forum you folks have here. I'm looking to share some information as well as learn from everybody here. I am getting ready to put the finishing touches on my DIY geothermal installation. House location: Just north of Ottawa, Ontario. House size: 3400 sq. ft. Heat loss per Manual J: 90,000 BTU Heat gain per Manual J: 22,000 BTU Basement has 2300 sq. ft of in-floor radiant. Kitchen/Entry area has 750 sq. ft in ceiling radiant using aluminum plates. 3 Hydronic fan coils supply the rest of the rooms in the house. All ducting over-sized to supply large volumes of low temperature air. This is a water to water system. After shopping around for an appropriate heat pump I think I will probably go with a 6 Ton Geostar (Made by WaterFurnace) GSW075R. My house is built next to a large deep lake. I was going to drop some piping in the lake but found out that getting a permit to do this is a complicated and next to impossible feat in Quebec. Here is the solution I came up with. If I can't put the pipes in the lake, I'll bring the lake to the pipes ! I know I could have just done a simple pump and dump, but closed loop seems more reliable and less problematic. I buried two 1200 gallon concrete holding tanks. Inside the tanks I have placed 300 feet of 1" copper tubing. I drilled two 4" holes in the tanks. 1 to drain the tank, and 1 to feed the tank and supply the copper coil. 4" PVC made a nice conduit for 3 x 1" plastic pipe. My drain hole is at roughly 3/4 of the tank, so my capacity in effect becomes 900 gallons. The bottom lake water temperature in the dead of winter is 40 deg. F During the coldest days, the geo unit is capable of roughly 67,000BTU with a COP of around 3 with a 40 deg EWT. I figure each tank needs to supply roughly 23k BTU for every hour of run-time with a temperature drop of 1.8 degrees per tank. So, I need to replenish the tanks with 900 gallons every hour so I don't freeze them up solid if running full time. Here's where I need a bit of help. I have 150 ft of head from the bottom of the lake to the tank(s). Since I don't have a need for pressure, can I run the submersibles without a pressure tank ? Will the (Myers Predator or Rustler) 3/4hp 20GPM pumps survive 24/7 pumping during the coldest days ? Here are a couple of pictures of my current setup. Marc.