u/Excellent-Sky8079

My T&P valve has been leaking drips here and there (only during heat cycle of the water heater). I believe that I need to add a 2GAL thermal expansion tank on the cold side of my (40GAL) water heater, but I wasn't sure what pressure I should set the bladder to on the tank, since it is not a constant pressure. My well tank is set 38/58 for my 40/60 switch. Do I set the expansion tank at the low end or high end?