I have a Tarm Scandic Solo plus 40 and also have 2- 220 gallons of pressurized water in my basement now. I live in Thornton NH and on cold nights below 0 i only get like 6/7 hours out of a full burn cycle. My house is brand new with spray foam insulation (so i cant do anymore insulation). My basement is full and i have no more room for pressurized tanks (that would be ideal the 220 tanks are awesome). I have seen people put septic tanks in the ground and put loops in the tank. I didn't know if anyone on here has seen or used this method. If anyone has any information and you would like to share please let me know. How long of loops did you run? How big of a tank? Did you line the inside of the tank? Did you insulate the outside of the tank? How did you connect it into the boiler loop? Pics?