Leaking air vent valves - hot-water system

Tony Shupenko, PE

I've been called into a completed project that has a variety of problems that we are in the process of troubleshooting. However, one has me stumped as to the cause. The client claims that many of the "Amtrol" automatic air vents, which were throughout the system (at hot-water coil assemblies, in the attics, which serviced the air handlers) leaked within weeks to 1 year after the project was complete. I do not know how the initial leaks were handled by the installer; however, just recently the client had another contractor replace all air vents with small manually operated ones (I have a concern about these as well). Anyway, after this long winded message, my question is does anyone have any ideas why so many air vent valves leaked? Since the valves were not available, I could not inspect them - from the description of the client, it seems that the valves leaked somewhere at the top, though I do not know if it was from the air discharge or from the casing. Does this sound like a manufacturing problem or something that went amiss during the installation?

Bob Bona_4

first clue

and a very bad idea-air vents in the attic. Probaly antifreeze in the system. And here we go again with another hydronic system that will very likely meet an early demise from antifreeze destruction bought on by neglect and ignorance.

These air vents (Hyvent is the trade word) are prone to leakage from debris in the system-or gum from aggressive antifreeze-or tough water conditions. They should and could be kept to the minimum..ideally, if the boiler was piped correctly, only one needed at the boiler. The others are pretty much worthless and will be a lifetime of replacement and leakage headaches. Sounds like that was taken care of. Remember, we are talking about a tin part that costs under ten bucks!

The solution is to be sure the circulators are pumping away from the x-tank, the boiler water is fed at that x-tank, and there is a air separator at the x-tank location. If you HAVE to use antifreeze, be sure the concentration and inhibitor levels are correct and they will need to be monitored at least once a year. Better yet, look into a cycling control to get out from under the whole antifreeze mess altogether.



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J.C.A.

Bob,

Truer words have never been spoken !

Food grade anti-freeze is mostly sugar based. When heated it seems to turn into molasses, plugging all the parts that it shouldn't and festering into a a menice where it matters the most(auto vents).

I wish I had a dime for all the "Spirovents" I've disassembled to remove the goo built up in them due to antifreeze. I'm also a big fan of the "exercise option" now available to us for keeping a system from freezing.It works !

You state that only 1 vent is needed in a properly installed system. You are right , but some folks just don't get that, still. Chris

Tony Shupenko, PE

Bob:
Thanks for the insight. Some other information I found out:
1. No anti-freeze in system.
2. System had a pipe burst this past winter.
3. Contractor was not well-versed in the plumbing trade (soldering, etc), as evidenced by many defective sweat joints in the boiler room (could there be debris flying through the system?)

Any additional insights?

Tony

Bob Bona_4

looking

back at my post, I guess I came off a little strong but man alive, it just is so heartbreaking to see every gasketed component, and even some sweat joints destroyed by an installation with no foresight to service and durability. A little planning can avoid major issues down the road.

Now on to your question:)

Sounds like the old "good news/bad news". No antifreeze-good. Freeze-up-bad. Candidate for circulator cycling for freeze protection-definitely. The service crew will love you for making their jobs a little-no, a LOT, easier. Debris in system? Maybe, but I'm more inclined to chalk this one off to SOP where Hyvents are concerned. BTW the high limit on the boiler is 180 max? If the limit is too high, and the Hyvents are all over the place, that'll kill them in short order too (steam). It doesn't surprise me to see Hyvents go bad in 2 years. Some don't even leak, they just sit there like stupid waterlogged tin cans and don't operate at all.

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Bob Bona_4

makes

you want to cry, doesn't it?

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Jerry Boulanger_2

Auto air vents installed anywhere but

on an air separation device will not likely vent much air unless the pump(s) are off. The water velocity in the pipes will carry the air right past the AAV. I agree with the previous posts - only one good quality auto air vent on the air separator, and manual vents at the high spots.

Dave Stroman

Spirovents

I have trouble with spirovents gumming up even when there is not antifreeze in the system. Looks like flux in the system cools at the vent and gums up the thing. Had to take a few of them apart and spray them with solvent to break up the gum.