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dangerouswithtools 02-23-2008 09:48 AM

air in baseboard heating pipes
In just the last few weeks we've gotten air in our baseboard hot water heating pipes, there's gurgling noise in both circuits when it starts and then again when it stops circulating. We haven't had any work done in several years other than annual boiler cleanings (last one in the fall). The gauge says 18psi, which is what it's always been. Any idea why it would suddenly develop air after all these years? There's no sign of leakage. Could I have a problem with the expansion tank? We're in a splitlevel house.

redline 02-23-2008 12:20 PM

Have you bled th system?

Boilerman20 02-23-2008 02:49 PM

air in lines
there are many ways air can enter system small leaks bad seals like circulator flange gasket seals even the mechanical seals in the boiler sections them selves that join the multiple sections another way is make up water usually when you have an expansion tank problem like water logged your boiler pressure rises and u start leaking out the pressure relief also depends on expansion tank type

NateHanson 02-23-2008 02:49 PM

Air can collect in the system as it comes out of solution in the water. (When water is heated, gasses dissolved in that water have lower solubility in warm water than in cold water, so as the furnace heats the water, air can be created.) Just bleed the system, and you should be fine.

dangerouswithtools 02-23-2008 04:37 PM

Thanks, now I know its not the expansion tank. I bled some air today out of both the upper and lower level circuits. The upper level doesn't have very much pressure, the water dribbles out, while on the lower level it's a projecting stream of water. Any idea what psi I should have in the system? I pulled on the lever that allows water into the system and I can hear some water moving in, but it doesn't sound like much and the pressure gauge isn't moving.

redline 02-24-2008 02:03 PM

You will have to bled it a few different times to get the air out.

Is the psi gauge working?

Is there an auto fill on this unit?

dangerouswithtools 02-24-2008 02:19 PM

I guess it's an autofill, it's right behind a backflow preventer on the water source line. It has a spring loaded lever that you lift and water enters the system. The psi gauge moved up a little bit when I opened this up for a minute or two. It has a threaded bolt with a flathead screw top that is secured at the bottom with a nut, I wonder if that controls the pressure.

Boilerman20 02-24-2008 06:26 PM

yes it is an autoflow usually boiler pressure is 12-15psi

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