Hey guys... not a Geothermal expert (inherited a Geocomfort system when I bought my house) but trying to learn and need a little help with my DSH. My system has an unpowered buffer tank that ultimately feeds a NG tankless water heater. Both the tank and the tankless were about 15 years old and the tankless was starting to act up so I had my plumber replace them both. The new tank is a standard AO Smith 40 gallon electric (not wired) and the new tankless is a Rinnai RUR199in - everything piped exactly as before. Had no issues to start but we were in between seasons so the system was not running much. Now that we're running heat a lot more often, I am noticing pressure in the hot water pipes when I first turn the shower on in the morning. The pressure relief on the tankless is also opening and leaking on the floor. This was not happening with the old setup. I've bled the system and not seeing any signs of air. Also talked to my local service/installer and he didn't have any ideas nor did he seem very concerned. I've read a few times about a part that needs to be removed on the cold water inlet to the buffer tank but I have not been able to track down any specifics - could that be the issue? What needs to be removed? There is a check valve on the cold water side before the DSH/buffer tank tee, just as before. Thanks!