| I never have to drain/refill my conventional expansion tank (equipped with a ~60-year-old Bell & Gossett airtrol system). Is your tank becoming water logged? Is the system's pressure control going haywire or the relief valve lifting? If not, then I would leave it alone.
If you are having such problems, I would suspect something is wrong with the air-removal device that is supposed to direct air into the exansion tank.
Unlike conventional tanks, bladder-type expansion tanks do slowly lose their air charge over time.
Doug |