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How to raise the pressure on an early 1900's ARCO boiler
My daughter bought a home with a very old (early 1900s?) Arco boiler. Cast iron radiators on the first floor, fin baseboards (fed from the 1st floor radiators) upstairs. All of the radiators (including the baseboards) have been bled, but although main floor heats nicely, no heat in the upstairs. The pressure gauge reads 11psi and everything I've read says it should be 12-15 but I can't figure out how to increase the pressure. Any suggestions?