Air lock in 2nd-floor radiators

Eric Wurster

I have a 2-story house with a newer-model hot-water boiler, with cast iron radiators. I drained the system this summer to remove one of the radiators, and when I filled the system back up, I am now unable to get any water to the 2nd-floor radiators. When I open the bleeder valves, they actually suck air in, which is not good. Does anyone have any ideas that could help?

Brad White_203

What is your water pressure?

You need at least 12 PSI and that would get you about 4-5 PSI at the top of the system.

I would check your water pressure and adjust the fill valve accordingly.

Also, if your expansion tank connection point is located upstream of the circulator (pump), you very well could be sucking air into your system.

The only other thing causing a sucking sound like that is Ross Perot and this is not his year either.

:I

Eric Wurster

Water pressure

The water pressure is usually between 12-14 psi. It is a newer system, so the pressure automatically regulates itself. Whenever I open the bleed valves upstairs, it actually sucks air into the radiator, leading me to believe that either there is still not enough pressure, or there is not enough water being let into the system.

Oh, and the expansion tank connection point is indeed above the circulator pump. The pump is near the bottom of the boiler, and the piping leading to the expansion tank comes out of the top. Why would this allow air into the system, and if so how can that be prevented?

Eric Wurster

Water pressure

Oh, I forgot to mention in the other post, the fill valve doesn't seem to have any adjustment on it.

[Deleted User]

Pumps don't suck....

unless they are pumping TOWARDS the expansion tank, AND they are of a high head nature AND the system has an inherently high pressure drop.

Rule #1: NEVER attempt to bleed air out of a heating system when the pump is running.

Rule # 2: If you have the pump off, and you don't get air out of the radiator, it ain't an air problem. Quit wasting water and your time.

Rule # 3: (should be rule number one) ALWAYS pump away from the expansion tank, and if an older design of boiler, pump away from the boiler and your air problems will go away.

Rule # 4: 1/2 PSI per vertical foot of system elevation above the boiler, PLUS 5 PSI. I don't believe I've ever seen a non adjustable pressure regulation device except for the Amtrol fitting, which doesn't lok like a pressure regulating device :-)

Rule # 5: Buy a Brick from the host to support this web site.

ME