I have a house built in 1949 with baseboard heating (5 loops), and I don't seem to be able to find any bleeder valves at the baseboards themselves. One of the loops in particular is making an awful racket. I've watched a few videos on how to bleed this kind of system (with a hose), but I'm not clear on how to do that with my setup.

As far as I can tell, each of the baseboard loops only has a shut off valve on the return side. One of the five does have a valve on the feed side, but that's not the loop that's making all the noise.

I have pictures below that could help, but in terms of the general process, is it as follows?

  1. Shut off the boiler
  2. Close all the valves on the return side of the loops
  3. Attach a hose to the spigot on the return-side
  4. Open one of the 5 return side valves
  5. Presumably at this point water (and air) flow out through the hose, but perhaps I need to open the feeder valve now too? I'm not sure if I should expect the system to regulate the water pressure itself in any way...
  6. Once I have only water coming from those hose, shut the hose spigot and then the baseboard loop return.
  7. Repeat 4-6 for the other noisy baseboard loops

If the above is accurate, I'm looking for A. some clarity on whether I've properly identified the spigot I should be draining from in the pictures below and B. input on how to fill the system using the feeder valve (i.e. do I shut off the spigot BEFORE I close the feeder? Do I have to worry about monitoring the system pressure as I do this? Etc.)

Thanks in advance!


Here are the pictures showing the setup (I did my best, parts of the system are sitting between duct work so pictures were a bit tough...and forgive any imprecise naming of things, I took an amateur stab at it :) ).

I'm assuming the spigot labeled in the picture below is where I should drain the system?

Heating 1

For the sake of completeness, it's a two-zone system with a radiant floor loop, but I'm ignoring that here.

Heating 2

This picture reflects the nightmare that is all this stuff tucked between the ducting, the subsequent pictures might make it more clear.

Heating 3

There does appear (I think?) to be a bleeder valve for the whole system atop the compression tank, it's wide open on the thumb-screw on top

Heating 4

Same as above from the other side for clarity.

Heating 5

Here's the baseboard zone, post-compression-tank showing the run through the circulator, flo-chek, and split to the 5 baseboard loops

Heating 6

And finally here's the return from the baseboard loops showing the shut-off valves.

Heating 7

Regarding Freeman's comment, I'm challenged to find the pin mentioned. Best I can tell that bleeder just has a thumbscrew, and even when I take it all the way off there's just plastic threading (see below). Am I being dense?

enter image description here

  • 2
    Yes, that's an automatic bleeder. Sometimes they fail to be as automatic as they should. Try briefly depressing the center pin of the tire-like valve on top and see if you get air out, or water. If you get air, hold it until you get water. See here for a diagram diy.stackexchange.com/a/211007/18078
    – Ecnerwal
    Commented Jan 15, 2022 at 19:40
  • 1
    Dude, for your first question here, that was extremely well done!
    – FreeMan
    Commented Jan 15, 2022 at 21:47
  • That was @Ecnerwal that suggested bleeding the air from the valve, and, TBH, I don't see it in the pictures, either. Maybe he can point it out more specifically.
    – FreeMan
    Commented Jan 17, 2022 at 14:14
  • Normally there's a pin in the center just like a tire valve. Either that one's different or the pin is way down inside (which is still different than normal.)
    – Ecnerwal
    Commented Jan 19, 2022 at 2:54

1 Answer 1


So you found the "Bleeder" valve, congratulation.


It is missing the cap (or removed), and the question is is it still working or stuck.

Sometimes after long use there is enough dirt in the Bleeder to make the floater inside get stuck in the upper position ,and is no longer bleeding the air.

enter image description here

Here is the cross section of the bleeder valve with floater inside.

Simple test if bleeder is working...

Attach a balloon to the top. See if it blows up. It might pop if too much air. If nothing happens the bleeder is not working.

Simplest solution is to replace the Bleeder valve.

  • There is often another bleeder at the topmost section of each hydronic loop.
    – gbronner
    Commented Jun 7, 2022 at 2:30

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