I'm working on a 40 - 45 yr.
old hot water heating system, replaced the circ. pump but had to drain all the water out of the system 1st. as there were no shut-off valves before or after the pump/boiler. System was then refilled & set in operation but at a reduced boiler thermostat temp until I satisfy myself that the air/gas charge in the 1970's era expansion tank was not compromised via the draining down or has been depleted over the 41+ yrs. of operation. I'm sure this type tank has no bladder inside & hence separation between water & air/gas charge like tanks available today. Can anyone offer advice whether the system is still safe with the 1970's era tank - don't want to replace unless absolutely necessary.
Thanks in advance for any advice given.