When I turn on my heat, the pump attached to the boiler comes on but the pipes don't get hot and the radiators never do either.

I've bled them and believe they are hot water radiators (since there is a pump), so from what I understand sludge shouldn't be an issue.

  • Can you feel the pipe right after the pump to see if it gets warm while the pump runs?
    – mikes
    Commented Oct 17, 2013 at 23:50
  • 1
    Yes, I did that and the pipe doesn't get hot. What does that point to? Commented Oct 18, 2013 at 1:30
  • Is the boiler heating the water?
    – Tester101
    Commented Oct 18, 2013 at 12:19

3 Answers 3


We ended up bleeding the radiators, upping the pressure, and replacing the thermocouple.

After all of that, we discovered that flames had been shooting out of the front of the boiler and melted half of the valve, messing up the electronics for the pilot light.

We ended up replacing the entire boiler since it was 35 years old anyway, but the reason for the issue was the messed up valve.

  • Not the most common cause, but ... <smile/>
    – keshlam
    Commented Nov 15, 2014 at 15:59

Low water Air lock or circulator not working is most common problems. What is the pressure of system ? Should be around 12 cold 20 hot. Add water to system if lower. You may have automatic feeder.
Check for any air bleeder that can be open.

  • Pressure is about 10 psi cold. This is what is was last year and the radiators worked fine, but I'll try turning it up to see. Commented Oct 18, 2013 at 11:06

Currently, I live with my grandpa, after 7 years I have been pretty-roughly introduced to the concept of hot-water heating via the radiators surrounding the basement, first floor and second floor apartment. We have constantly had issues with this type of heating, as it is a dated system, but here is what I have come to recognize over the past 7 years of working with him to get the apartments and basement warmed up.

Chances are there is air in the radiators.

I would check all the air bleeders on the radiators in the given area.

Bring a small bucket, an old rag/t-shirt, and a flat screwdriver.

  1. Set the bucket about 6 inches below the bleeder, and say 6 inches out.
  2. Put a rag over the bleeder hole
  3. Gently unscrew the bleeders, this will open it up and water should spew out, not all the way, just enough so water leaks out.
  4. let it run, and allow the water to flow into the bucket, if it's in a not-so-easy spot for the bucket, use the rag to sop up any water coming out.
  5. Check for a steady flow of water, check if it's warm, check if it's spitting out initially or indefinitely.

I have come to find that initially it will spit out a few times, indicating there was water in the line. Let it run til it gets about luke warm, maybe not, room temp. If it never does, and the heater is on, then you can isolate the issues.

Hope this helps. Cheers!

  • Thanks for the comment, but we already bled them (as mentioned in the question). Commented Oct 19, 2013 at 13:18

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