Best way to remove air from fin tube baseboard system

Old 02-15-21, 06:26 PM
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Best way to remove air from fin tube baseboard system

My hydronic system has 3 zones with circulators. Last spring I wanted to get all the air out so I forced water through the 3 purge stations until it was a solid stream of water. All was well. As this winter heating season commenced I started to hear slushing, bubbling, and gurgling noises more and more in the pipes upstairs. The heat still works but the noise and possible decrease in efficiency is worrisome. I have tried opening a few bleed screws in the baseboards where I can get to them but they never hiss air out - only water comes out.

Yesterday, I looked at the boiler (Triangle Tube Combi) and there is no air elimination device anywhere in the plumbing. There are a couple of valves on top of the boiler that I cracked open but only a tiny amount of air came out. There is no air scoop or air vent near the expansion tank or anywhere else.

So what to do? I can purge through the purge stations again but eventually the air will separate out of the water again. Would a device like a spirovent eliminate this issue or is there some better way to get the air out upstairs in the baseboards?
Old 02-16-21, 07:05 AM
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Please show us wide-angle photos of the three purge stations, the near-boiler piping, expansion tank, circulators, and the typical zone piping and connections to the baseboards. What is your system pressure?
Old 02-16-21, 07:21 AM
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Make sure you have pressure in the system. Actually something like 10 or more PSI to make sure there is pressure on the second floor..

Can you elevate the end of the baseboard with the bleed screw and depress the other? (Do not use force, the pipes may be constrained by the holes in the joists.)

This may allow you to get a little more air out of the baseboard unit.
Old 02-18-21, 01:24 PM
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Air bubbles rise in hydronic system water to highest points of each zone. Zoneout might check with level to make sure vent is at high point of baseboard element.

Venting a lowest boiler level, with air scoops, purge stations or whatever … even with circulator on, and zone valves open is wishful thinking.

Basic physics ….raising water pressure to vent, decreases release of air from water. Air scoops work on principal that lowering flow pressure, by increaseing diameter of water passage promots venting. They are just an empty space.... no magic.

Purging station release whatever comes out when opened. Water rises so it is closed. Any air remaining at high places in zones is compresed by rising water to 12 psi, and not vented.

On DH home system each original 12 enclosed heating elements had manual vent valve. Each element fed from monoflow/diveter tee 18” below was guaranteed air trap.

In early years as home ower, tried many types of auto vents. Most failed to vent properly and frequently leaked and were not servicable.

Finally found solution with Watts auto vents. For $8 are very effective, reliable, can be opened fo servicing . For those worried about leaks, the black knob can turn off venting when sleeping.

Gaget like Spirovents, for $100 do not solve problems only add new ones. Venting is eternal need on hydronic systems that a reliable $8 auto vent does well

Last edited by doughess; 02-18-21 at 04:05 PM.

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