Hello all. Just want to make sure I understand my expansion tank. I redid my storage piping earlier and at the same time installed a new tank. B&G HFT-40V. I am having some high pressure issues with the new setup. I am getting over 30PSI at high temps. I installed the tank where the SETON w-90 originally had a small tank. Between the fill valve and a T fitting in the return loop to the system pump. There is a ball valve between the tank and pump along with a small drain setup between the tank and shutoff valve. Originally I brought the system up to temp (165) while draining the tank slowly as the pressure was rising. Kept the system PSI to 12. Then I shut off the fill valve supply. After the system cools to around 140 the pressure will drop to 0. Slightly open the fill valve for a few seconds and the pressure will rise to 12. Heat up the system again to 160 and run for a day. Try to heat system to 180 and the psi will rise to 30. I then turn off the ball valve between the pump and tank to drain some water. I only get out about 2-3 gallons before the tank is empty. I can then reopen the ball valve and the PSI will return to 12-15. I would think the tank should be holding around 10-11 gallons when the system has the high pressure. I have been through this procedure several times and still only drain 2-3 gallons when the psi is reading 30.