Almost all of the radiators (forced water) in my house heat up fine. However, a single radiator needs regular bleeding (~1/day) in order to heat. Note, this radiator is not at the highest point in the house (it's a split level; I'd say it's around 3/4 of the way up), and radiators higher up are plenty hot.

Also, there no obvious water/corrosion stains around this radiator.

What might be causing this problem, and how do I fix it?

  • 2
    Is the radiator at the end of a long run? Is it in any way different from the other radiators?
    – Freiheit
    Oct 18, 2012 at 20:38
  • @Freiheit I am not sure if it's at the end of a long run. There are other radiators on the same floor, but I'll try to trace the pipes tonight. To the best I could figure out, I think it's the same radiator as others in the house.
    – Eli Lansey
    Oct 18, 2012 at 20:50
  • 2
    It wouldn't necessarily have to be the highest radiator to collect the air, the pipes would have to follow a sort of upward route of least resistance for the air to collect in it.
    – Mark W
    Jan 11, 2013 at 11:31
  • 1
    This could happen if the radiator is the first one on the run starting from the boiler. The air will want to collect at a high point but if the pipe goes down after this unit then it may get stuck there if the flow is not fast enough to push it back down. You might consider that there is a leak that is letting water out of the system causing too much makeup water to enter, which will add the air. You could also think about putting in an air scoop between the boiler and this radiator to get the air out before it gets stuck in that loop.
    – Bob A.
    Feb 26, 2013 at 16:24

2 Answers 2


When you do your daily bleed of this radiator if you don't actually get air coming out, just water. You don't have an air problem, you have a water flow problem.

If your system a diverter-tee system (a "one-pipe" system), check to make sure that the tees that feed this radiator are installed the same way as the tees that feed your working radiators. The diverter tee for this radiator should be on the return side, and the stripe (or other indicator of orientation) should be between the branches. An incorrectly installed tee could cause the exact problem you're describing.

  • Your questions are not an answer. They belong as comments to the question.
    – ShoeMaker
    Mar 13, 2013 at 11:45

I can't say for sure what might be causing it but if when you bleed it you do get air coming out a simple fix may be to install an automatic bleeder. These are screw in replacements that go where the existing bleeder screw is. You adjust it so that it is just tight enough to not let water out, and the idea is it will automatically release small amounts of air. How well these work is debatable, but it might be a $6 fix to your problem. I grabbed a few of these : http://www.homedepot.com/p/Plumbers-Edge-Automatic-Air-Valve-PE970/300011259

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