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Top floor radiator not getting hot. (solved)

weil_fail Member Posts: 81
edited November 2018 in Radiant Heating

so, I have a hot water radiator heat system. the top floor radiator was not getting hot. I figured it might be air in the system. I opened the bleeder valve slighly and some air started coming out. great! I thought. problem solved! but then the air stopped and there was nothing coming out. no air, no water. the other radiators still work. does that mean I'm low on water?

is this something a handy homeowner could do, or is it difficult? I've replaced igniters, relays, main control boards on boilers before, but never added water. is youtube university enough to figure out how to add water?

here is the gauge and boiler setup:

Solved: needed more pressure since the rad was 4 floors above the boiler. ~24 psi got it done.


  • SuperTech
    SuperTech Member Posts: 1,919
    edited November 2018
    Hmm. Your gauge shows adequate boiler pressure, but it might not be accurate. I didn't see anything but do you possibly have multiple circulator pumps or zone control valves? Does the pressure on the gauge change if you drain some water out of it?
  • weil_fail
    weil_fail Member Posts: 81
    here is what looks like the fill valve:
  • weil_fail
    weil_fail Member Posts: 81
    SuperTech, I'll go tap on it and see if it changes. I thought it was weird also that I stopped getting air but the gauge wasn't low.
  • Maybe tapping the old gauge won’t be enough, so why not screw a new gauge onto the boiler drain, with appropriate fittings, and then you will know what’s going on with your system pressure.—NBC
  • SuperTech
    SuperTech Member Posts: 1,919
    I always carry a very cheap gauge with garden hose connection to check pressure.

    With the fill valve that you have you shouldn't have to "bleed" the system by draining water. You need to "purge" each zone by pulling up on the fast fill lever to increase the pressure and force water and air out of the zones. Just don't forget to put the fast fill lever back down after you finish the purge. Always pay attention to the pressure gauge while purging. Avoid allowing the pressure to exceed 25 PSI during purging. Once completed you should try to bleed any remaining air out of the radiators.

    Hope this helps 😉
  • neilc
    neilc Member Posts: 2,196
    when you bled the radiators, was the circulator on or off?
    it looks like you're pumping towards the boiler, and then the tank,
    if the circ was running you effectively lowered the pressure up at the top rads,
    If the circ was pumping away you would have maintained pressure upstairs.

    known to beat dead horses
  • weil_fail
    weil_fail Member Posts: 81
    hey guys. I indeed needed more pressure. I had to get the pressure up to about 25PSI before I got all of the air out of the top floor. which kind of makes sense. it's a 4 story house.

    thanks for all of the help