my radiators (steam heat) clank and hiss. how do i fix this?

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  • 1 decade ago
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    This is one of the reasons that steam heat is not widely used anymore.

    First: The hissing you hear is the air in the heating pipes as well as the radiator being pushed out by the steam in the system. At one end of the radiator there is a small valve, it sometimes looks like a round disc with a little nub on top, or a small cylindrical piramid.There is also a small hole on top, this is the vent which must be clear so air can pass through it. These valves must be pointing up towards the ceiling, as in the little nub or the top of the piramid.

    Second: The threads on the valve must be secure either with thread compound or even better Teflon tape. The valves don't need to be wrench tight, just secure enough so that no steam or liquid leaks out of the theads.

    Third: The radiator needs to be pitched away from these valves. This can be done by putting a level on the radiator and then shims can be put under the legs, or base to pitch it properly. You can use any kind of shim, my favorite way is to use pennies in a stack. The pitch will allow the water to flow back to the boiler when the radiator is cool. If any water is trapped in the radiator or the pipes leading to it, it will cool and the next time the steam comes in contact with it you will hear the clanking again. This may also happen if you have to much water in the boiler, or if there are a lot of minerals in the boiler water which could make the water surge up into the pipes. If this is the case , your heating man can either try to skim the minerals out of the system, or add chemicals to the boiler to help calm the surging.

    Last but not least the radiator should work as follows: When the thermostat calls for heat, the boiler will run to make steam, as the steam rises in the system it will flow to the radiators with the largest vent hole first (some have numbers or letters on them ei: A being the smallest B C + D being larger and so on) . As the air is pushed out of the radiator you will hear the hiss, this is normal. When the radiator is fully hot all the way across the hiss should stop. Periodicly the valve will click open and closed through the heating cycle alowing a small amount of steam to be released.

    If a radiator hisses continuously and nerver stops, chances are the vent is not closing and should be replace. If you choose to make the repair yourself make sure the heat is off, and allow the system to cool down first. Steam can cause severe burns so be very carefull, or better yet have your plumber or heating man do it.

    Source(s): I am a retired heating technician with thirty years of experience.
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  • 3 years ago

    Radiator Hissing

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  • 1 decade ago

    SOUND'S LIKE YOU HAVE AN AIR LOCK.YOU CAN BUY A RADIATOR KEY WITCH FITS IN AT THE TOP USUALLY ON THE RIGHT HAND SIDE,JUST GIVE IT A COUPLE OF TURNS AND IT WILL RELEASE THE TRAPPED AIR, BE CAREFUL NOT TO TURN IT TOO MUCH AS THE BOLT CAN COME OUT.

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  • 1 decade ago

    I would add that it may be wise to have a pan of some sort underneath in case you let water out as well. If you've ever bled auto brakes, it's about the same process.

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