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noisy air valves on steam system

I have 2 steam radiators  (far from boiler) that were making hissing noise from air valve, i pitched the radiators correctly, loosened  the nut to take out any extra water from the radiators and replaced the air valves with hoffman #40 and the hissing got better but it still makes noise. any answers?


  • kcopp
    kcopp Member Posts: 3,657
    edited April 2010
    well sounds like.....

    that there is not enough main venting on the lines in the basement.....Do you have any OR are they undersized or plugged? How big are these rads?

    Whats the system pressure? kpc
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