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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?


  • Leon82
    Leon82 Member Posts: 684
    If there is no water feed to can use a washing machine hose to force it in thru a boiler or zone drain
  • lchmb
    lchmb Member Posts: 2,997
    should be an auto fill if you were bleeding and it maintained pressure.. some pic's may help to locate it..
  • thechelstroms
    thechelstroms Member Posts: 3
    So if I'm understanding you, just adding water to the boiler will increase the pressure?
  • Big Ed_4
    Big Ed_4 Member Posts: 2,518
    There should be an pressure reducing valve feeding water into the boiler ... It comes in though an 1/2" water line and will look like an bell .. The more modern models will have an lever for fast filling ... Becareful the pressure relief valve with pop open at 30# ... Try a fast on and off with the lever ... If loose either its plugged or the shut off before is closed .. On top of bell there will be an lock nut to loosen adustment screw.. screwing down will increase pressure.. Hope this Helps
    I have enough experience to know , that I dont know it all
  • Leon82
    Leon82 Member Posts: 684
    > @thechelstroms said:
    > So if I'm understanding you, just adding water to the boiler will increase the pressure?

    Yes it will.
    You can look for a line from the cold water supply that goes to the boiler. This should have the pressure reducing valve on it. Follow the piping there probably is a valve before or after it.
  • STEVEusaPA
    STEVEusaPA Member Posts: 6,368
    Even though this can be an easy DIY thing, I think it best if you have a qualified tech come out and go over the system, and show you how to properly bleed and purge of all air.
    You're going to need someone for annual maintenance and repairs, why not pick someone, let them (and you) get familiar with the system, before it gets too cold and/or you have problems.
    The gauge could also be bad and stuck on 11. Then when you add more water, you're going to have problems.
  • delta T
    delta T Member Posts: 883
    are we sure the problem with the upstairs heating is due to lack of pressure? If you open a bleed valve upstairs, do you get water out? When you say

    "Cast iron radiators on the first floor, fin baseboards (fed from the 1st floor radiators) upstairs."

    how exactly are they fed? did someone just put a tee ahead of the supply and one after the return for the CI rads, with pipes going from those tees to the fin tube upstairs? I think that something is fishy about how this is piped, and that is the more likely candidate for the baseboard not working upstairs. is there only one pump? Are there zones or just on big zone for the whole house (how many thermostats do you have)?
    Mark Eatherton
  • thechelstroms
    thechelstroms Member Posts: 3
    When I bled the valves upstairs water came out. And there is only one thermostat in the house. I did read that tees in the piping system cause problems. However, you cannot see them as they are in the ceiling/floor.
  • Grallert
    Grallert Member Posts: 597
    I very much doubt that the problem is a lack of pressure. If your gauge is correct or even close you have plenty of water pressure to reach the top floor of most houses. Plus you have water at those radiators. Your issue is elsewhere. Could simply be the location of the thermostat, could be a valve, could be a pump assuming this is a pumped system and not a gravity system. Too many assumptions, not enough info. Could you take pictures of the radiators and the boiler? That would be very helpful.
    Miss Hall's School service mechanic, greenhouse manager,teacher and dog walker