That one weird trick to bleed radiators that plumbers hate!

January 5, 2018 10:54 AM

I have a toe-kick (under counter) radiator in my kitchen that was installed wrong--supply and return are reversed. It seems to be air locked, but the bleeder valve is on the flow line, so opening it up just results in water pouring out. I'll get it replumbed eventually, but do you have any ideas how to get the air out (short of using a saddle valve to poke a hole in the actual return)?

This is the model I've got.

The manual clearly provides that the lower pipe is the supply, and the upper the return; but whoever installed it (13 years and two prior owners ago) mixed it up. It shouldn't matter which direction the flow goes through the manifold, provided you don't have to bleed it. But I have to bleed it.

All the circulating water is behind the bleeder valve, so if I open it, I just get water coming out--not the air.

I've had a plumber take a look while on a call for something else, and his proposal is to drain the radiator system, re-plumb the lines correctly, and add isolating valves to each line. I'm 100% agreed and down for that--but he didn't have time today, it's cold and I don't want to drain my radiators, and his quote was high (but his company handles my new heating system, and I'll probably just go with their quote).

I could add a saddle valve to the actual return, but I don't want leaks under the cabinet where I might not see them. I've already given the thing a bunch of love taps to try to dislodge the air, but no dice.

So, I'll surely pay to have this done right at the end of the season--but do you have any other ideas of things I can do now to get this going?

The radiator is on its own little loop; there are no upstream or downstream appliances to bleed.

posted by Admiral Haddock to Home & Garden (2 answers total)

If it's on it's own loop are there any unions at the return to the boiler? If you could loosen one enough for a bit of air to escape that would do it, I think. Allowing air to escape anywhere on the return line should take care of it, and since it's on it's own loop you can treat the entire return side of the loop as the return side for that radiator.

Related to that, would you be open to adding a saddle valve at the boiler return? Should have the same effect, but at least that way if you have a leak it would be there - if it's unfinished space or has a drain maybe that would do it.
posted by true at 1:10 PM on January 5, 2018 [2 favorites]

How about turning the whole thing off, and closing the return line at the circulator if you can? That will allow any trapped air in the unit to bubble into the pipe next to the bleeder valve without having to fight water pressure generated by the circulator.

Then open the bleeder valve and turn the circulator on again right after you've opened the return line again; at that point any air in the pipe with the bleeder valve on it will be blown out the bleeder valve before water starts coming out.

If this works at all it may require several iterations.

As I read the diagram in the IOM manual, the individual radiator contains four little independent loops, each with its own separate connection to the supply line and return line, and it would take quite a bit of air to block all four.
posted by jamjam at 3:04 PM on January 5, 2018