What Does It Mean When My Boiler Pipes Gurgle?

Symptoms

• If you hear gurgling in your pipes, it may seem to be located in one spot or be moving through your pipes, bubbling and churning along. What you are hearing is air trapped in the pipes.

Source of Air

• Heated water expands, creating pressure in an enclosed system. If your boiler and pipes had no way of accommodating the pressure of expanding hot water, the system would blow out. To prevent this from occurring, boiler systems have a pressure relief tank that contains air. Expanding hot water that enters the tank compresses the air inside. The tank has a valve to release the air pressure when the tank fills with expanding hot water, a potentially dangerous situation. If some of this air gets into your pipes, it will make a gurgling sound as it moves harmlessly through your system.

Treatment

• Air is lighter than water; so if it escapes the expansion tank, it rises through your pipes and collects at high points. Boiler systems typically have a small “tire valve” at the high places where you can “bleed” or release air until hot water, not air, flows from the valve. If your system does not have these valves, you have to turn off the system, drain the water and refill it.

Prevention

• Install air eliminators that automatically bleed the air from your system as it collects in high points. If no air is allowed to collect, you won’t hear gurgling.