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Had to do an emergency pex repair on a section of the lines for our in-floor heat, and afterward, could not figure out the best way to bleed the lines. It was clear the way the temp shot high and the boiler cycled off (and the circulator was hot) that the system was airlocked, but I could not for the life of me figure a decent way to attach a drain line in order to bleed the thing.

I ended up isolating the lines one by one (a major PITA with these weird old WIRSBO manifold valves that have a plastic disc that takes a plastic cap/wrench to turn them) and then popping the center seal on the circulator pump and listening to the air gurgle out of there.

It worked. Just took a long time. (The line that needed a repair turned out not to be the only one with some air in it.)

Makeup water / fill side water comes into the top line from behind, which is the return, heading back into the boiler from the return manifold. You can see the half inch copper coming in. There's no shutoff on either side of it. Similarly, no shutoffs on the supply side pipe lower down.

The only spot I can think of to try and attach a bleed hose would be the empty return-side bib on the top manifold, but there's uninterrupted pipe from there to the input from the fill/makeup line, I thought "that's not going to work."

System is running fine and keeping the place plenty warm with usual cycling and fuel use, so it's all good for now, but I want to be able to get a bleed done before heating season a bit more easily in the future if I can.

What's the obvious thing I'm missing here?

Giving serious consideration to having a tech install newer manifolds and proper shutoffs / bleed ports over summer when things are calm.

hydronic manifolds view

hydronic boiler side view

EDIT:

This is the supply/return loop manifolds in the garage. Something like this should would have been handy inside. (This system is mothballed since the boiler itself was inoperable and we don't need heat out there at this point. We just filled the lines with RV antifreeze.)

enter image description here

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  • BTW, I inherited this system with home, didn't install or have installed myself. For all its corner-cutting, it at least works pretty well, keeping a cabin in a very cold location warm all winter.
    – user122950
    Jan 23 at 14:58

2 Answers 2

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You current bleed setup is a plain T with a automatic purge valve on the top side. Unscrew the cap on top to start bleeding.

enter image description here

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  • There are 2 autovents. (One is atop the boiler.) They were clearly inadequate to do a bleed of large amount of air all at once. I tried that route. Pulling the center screw seal on the circulator worked far better. The one you've circled there is <2 years old, set precisely at manufacturer's recommendations (the box with instructions is tacked to the wood behind the system, and I marked the valve's plastic adjustor with nail polish so that counting 3 turns is easy.)
    – user122950
    Jan 23 at 16:51
  • @WPNoviceCoder To improve it's bleed rate you can replace the simple T connector with a "air scoop" which has a larger chamber that lets the water flow slow down so the bubbles suspended in the water have a chance to settle out. Jan 24 at 9:31
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i'd cut everything out and re-pipe it cleanly and properly using valves to allow for bleeding the system with the bleed located in the correct location.

What's the obvious thing I'm missing here?

ball valves on each line off the supply manifold.

and not pumping into the expansion tank, and depending where your automatic fill valve is (i can't see in the pic) that may be a problem too, and a good air separator.

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  • The fill/makeup is the half inch line coming in from the back, just to the right of the expansion tank, which flow is heading to the right also, then down into the boiler.
    – user122950
    Jan 23 at 14:57

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