Baseboard Heater - sucking sound when bleeding air

Brad White_191

No, you probably do not have Ross Perot in your piping :)

I would suspect that your expansion tank is connected to the discharge side of your circulator (pump). Is this the case?

When this is done and especially if the piping is small-bore with respectable pressure drop, often the suction side of the pump will draw a vacuum, sucking in air whenever it can. When you open the vent with the pump running, this is what can happen. With the vent closed, valve stems, threaded joints and other imperfections which are normally water-tight, can draw in air in small amounts over time. These add up.

I suggest you take a look at where the expansion tank connects and relocate it to the suction side of your pump.

If you have multiple pumps on the return side of the boiler, you may have to move those to allow a common upstream connection location.

The fact that this has been recurring leads me to think this.

Dana_8

bleeding air from baseboard heater - sucking sound?

We have a baseboard water heating system and have been having loud, gurgling sounds running through when it kicks on. In the past, when this happens, we have bled the air (only one bleed valve for two zones - one zone upstairs, one downstairs - valve is downstairs) doing so until only water comes out and it has worked perfectly. This time, however, when we are bleeding there is air coming out as usual, but then it pauses and it sounds as though it is sucking air in, then will return to spitting air and water. We can't seem to get the air out, despite repeated attempts at bleeding. And it is very, very loud, waking us up at night. Advice is appreciated.

Dana_8

RE: That giant sucking sound..

Thanks,we'll check that. I should clarify that the reason we had air in the system the last time was because the pump was leaky. We replaced the pump a year ago and have had no problems until a month or so ago...

Thomas Mörtberg

A common problem is low pressure in system.