Many factors cause gurgling radiator

Q I have a radiator in my house that gurgles. It sounds as if water is running. The other radiators don't make noise. I have bled the radiators and had the whole system balanced out to ensure that the pressure is correct. What is causing this and do you have any suggestions on how to keep this radiator from gurgling every time the heat cycles on?

A Most of the time, gurgling radiators are caused by accumulated air and bleeding them solves the problem. Sometimes, however, as houses age or are remodeled, there may be some sagging of floors or supports that can alter the "level" of the radiator, trapping air within the radiator, according to state energy specialist Phil Smith. Older, larger radiators also can simply sag over time. (Place a level atop the radiators to check their positioning and level. Fix these as needed.)

In addition, Smith said that valves on older radiators, assumed to be open, are only partially open. When the pump starts to drive water through the system, a bubble of air forms as water flows over or around an irregular surface in the radiator. That can produce a "gurgling" sound. Have a contractor check it.

Also ask if the pump speed is too high, which could cause gurgling. Ask if an "auto bleed" or "AirTrol" device, which automatically removes air, would be a good investment for your system. Have the piping to the radiators and the area around the radiator valves checked for any evidence of water leakage.

Remember, when "bleeding" radiators, let the water flow a bit to be sure you've removed all the air possible. If this does not work, wiggle the radiator a bit and see if it dislodges any air. If you need to bleed radiators frequently, it is usually an indicator of a problem with the expansion tank or elsewhere in the system.

The expansion tank provides a cushion of air accommodating the change in volume of water as it is heated and cooled. The expansion tank should be a third to half full. If it is full of water, it needs to be "recharged." If you have never done this yourself, hire a heating contractor and ask the technician to show you how to care for your boiler and expansion tank. Make sure you're shown how to properly add water to reach the desired system pressure. Taking notes and capturing these details with a camera can make future care easier, Smith said.

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