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Whistling Rads after Boiler Cuts Off

MeganB Member Posts: 2

I’m new here. I’ve been trying to read other posts here to help troubleshoot our rad issues.

I purchased my home last year and we have a steam boiler system single pipe with 6 rads. 3 on first floor, 2 on second, and the third in the attic. I’ve been told my boiler is much larger than I need for my home but it was here when we bought it. No main vents. We were losing water and filling our boiler at least weekly. We’ve since replaced all air vents and now we are refilling maybe once a month. However, with the new vents they seem to be quite noisy. The whistling happens after the boiler cuts out, almost like the air is getting sucked back into the system. Any way to reduce/eliminate this or is that the result of us lacking main vents? 

I appreciate the insight!


  • Big Ed_4
    Big Ed_4 Member Posts: 1,970
    Where did you buy the vents and what type ?
    I have enough experience to know , that I dont know it all
    EBEBRATT-Ed Member Posts: 12,654
    Completely normal for the air vents to suck air back into the system. I would suggest having main vents installed if you have none. It will save fuel and reduce (but not elemenate) the radiator vents from whistling when the boiler shuts down.

    I would suggest looking at "find a contractor" on this site. And post your location, someone may have a contractor they could suggest. he could install vents, fix any leaks and optimize your system.
  • MeganB
    MeganB Member Posts: 2
    We purchased the air vents online. They are all Hoffman 1-A. Still unsure how to “set” them based on the location of the air vent (1st floor compared to 3rd) so they are all set the same to medium/3. 
    EBEBRATT-Ed Member Posts: 12,654

    You need main venting if you do not have it the system will not work well. Start with all vents wide open. Then any rooms that overheat you adjust them downward towards closed. make small adjustments at a time as adjusting one can affect others

    You should install main vents first