air in the hydronic heating system

I have some air in my hydronic heating system. Not much. Not enough to create an air block. Not enough to hear it on the first floor. Just enough to hear some running water whooshing sounds on the second floor where water pressure in the system is the lowest.

I think I introduced the air into the system when I chemically flushed it few years ago when I was addressing the ketling problem. I don’t think I actually added air into the system, but it rather gased out from the make-up water.

I do have a simple air eliminator in the system – Bell & Gossett Model #97. It’s screwed directly to the boiler heat exchanger. See pic below:



I’m pretty sure the air eliminator is dead. There is some rust around it implying it was working at some point in the past, but it’s been bone dry for the last few years.

I see few choices…

1. Purge the air with a water filled bucket and a pump. Basically cycle the water thru the open water in the bucket allowing the bubbles to escape. Should work, but it will introduce some new water into the system. Also I lose about 2-5 psi per year, so I keep adding a bit of water every year or so, so eventually I will have the same problem.
2. Fix the air eliminator. I don’t have an easy place to cut in and install the new air scoop. Nor I really want to cut into the system. And I’m afraid to replace the existing one since it’s directly screwed into the exchanger and I don’t want to compromise that joint.
So I was thinking replacing the guts of the air eliminator could be acceptable alternative. It looks like the top could be screwed off and I could simply swap the guts with a new one. I think I could try to affix the body of it somehow and take the top off without putting too much stress on the eliminator/exchange joint. Is anyone familiar with this model and can confirm the guts can be swapped?

Thanks!

p.s. and here it a stock pic of the little guy:

 

Is the black cap loosened? If it's tightened, the air eliminator won't function.

Losing any pressure over time isn't normal. What is the pressure on the boiler now?

I don't understand your idea of purging with a bucket and pump. Why a pump? What have you tried so far for removing air?

 

the cap is loose of course.

the bucket idea is simple. fill the bucket with water and put a pump into it. fill the pump hose with water and connect it to one of the drain valves. connect a hose to another drain valve and put the other end of the hose into the bucket under the water.

open the valves and pump the water from the bucket thru the system and back into the bucket. the air in the system will travel into the bucket and bubble up, while pump will be sucking air free water back into the system. except of course there is some dissolved gas in the water.

few pounds loss of pressure in the the system per year is not my concern at this point. the pressure is ~20 psi.

 

You probably have another bleeder valve in your system . . . . maybe up in the living quarters (at the highest point) ?

This B&G Air Vent looks remarkably similar to this Taco Vent (Made in Italy but no Model #) that I recently removed and cleaned up:



If your B&G is similar (like in identical), then the "guts" aren't much more complicated than a float similar to what you might find in a carburetor, except when the float sinks, it means air has been captured and it's supposed to let air out until it the Float rises and closes the valve:



You can probably bleed yours by manually opening the little cap to relaese any air, and close it back up tight if any water appears. You might need a straight pin (I use a Turkey Breast Pin myself) to push the valve open manually.

Sometimes the valve gets crudded (sp?) up with mineral deposits and ceases to work altogether, and some people leave the little cap on tight all the time just in case the valve gets stuck open, and leaks all over the place while you're not looking.

Many such air vents are not serviceable at all, and cannot even be opened up at all for an examination/cleaning. They're permanently sealed and it's expected that they'll be tossed when they get clogged.

Your Post makes my effort in already having this one ready to go worthwhile.

You can probably locate another place to install such a Air Vent that is a little more convenient . . . . just in case you can't resuscitate this one.

 

Vermont,

I think mine could be clogged up as you're describing. I can remove the cap and nothing happens. No air, no water. It is a floater type and it looks very much the same as the one in your pics:



Can you push the valve down with a needle thru the opening that is under the black cap? I think that's what you're implying, right? i could try that.. but should I reduce the pressure down first? i don't want to get a hot stinky water spray in my eye

i was thinking about waiting till season is over before doing any of the servicing..

no other air scoops anywhere. i'm intimately familiar with the whole system except the parts that are in the walls. no desire to cut into the system yet. it's 32+ years old, so i try no to disturb it as much as i can

 

Yes, I just pushed the spring loaded valve down (open) on the loose unit I have in the photo, and the total movement is only about ⅛".

To avoid that "squirt in the eye", you can align your pin first and then put a towel over the unit to block any such hot squirts.

If yours has a lot of mineral deposits holding it shut, it may not budge; and if it opens the accumulated air will exit first followed by water. If the spring doesn't shut it off, you'll have to put the cap back on tight immediately.

That's quite an elaborate procedure you've created for adding water to your boiler fluids. Are you on a pressurized Municipal water system that could be used to do the same thing, with a Automatic Fill Valve ?

 

If you must remove that vent reinstall it with a 6" nipple and a coupling instead of going right into the block which should have been done in the beginning. It will also work better and be more serviceable. you can even put a small shut off on the nipple so you will not have to drain any water in the future. Just a thought.

Hope this helps.

 

Vermont,

I'm gonna try the needle and the towel trick, but maybe at the end of the season. if it doesn't work, I will take it apart and attempt to clean up.

I do have cold water intake from municipal with all the appropriate valves. I just don't want to add the fresh water into the system - with cycling like that I will replace 100% of the system volume and that's what might've caused the air to be in the system in first place. Using the bucket will limit the new water intake.

I've tried similar trick when I need to add 1 gallon of inhibitor into the system and it works pretty well.

Spott,

Having a nipple like you mentioned would be very helpful. if i do remove the whole scoop, I will do that, but I hop I don't remove it.

Thanks for your help, guys!

 

Just so you know you don't have to remove the scoop to change the vent. Just take the pressure off the boiler, unscrew the vent and replace. You would find it easier to remove by taking the top cover off the boiler.

 

spott,

your message is a bit confusing since you're using the terms scoop and vent that could be used interchangeably.

i understand that removal of the air eliminator is not that complicated. i removed the boiler jacket in the past when i cleaned the heat exchanger.

my hesitation to replace the whole thing is that i suspect that the thread on the scoop/exchange could be rusty and i might need to use some force to unscrew the scoop. And last thing I want is for the boiler to spring the leak. Mid December in New England.

i had an unfortunate event with a hot water heater of a similar nature that ended up with me replacing the heater in the middle of the winter. So I’m a bit more careful with disturbing the peace nowadays

I’m tempted to try to clear the floater with a needle. I looked at the little cap on top of the vent and it looks like it has a rubber gasket inside and should hold the water if for some reason the vent doesn’t seal well after I clear it. But then the cap is plastic with a weak thread and I could see how I could overtighten it to the point it would break.

Homedepot seems to have a Taco HyVent air eliminator that looks very similar. Worst case scenario, I can partially drain the system, replace the vent, fill it back up before it gets too cold. Or I could simply wait sill spring

Pex supply has the exact model I have for $8. I might just buy that one, wait till spring and swap the guts. I suspect that my current one is all crudded up and needle trick would work temporarily only…

I think I might be overthinking it now

 

Diver,

Now I'm confused. First off SCOOP and VENT are never used interchangeably and are completely 2 different parts.

An air scoop is a fitting that helps separate the air from the water going through it and has an air vent on the top to release the air in the system. They are also called air eliminators such as a Spirotherm which is an upgrade from the regular air scoop and you need no hy-vent with it.

 

spott,

when you say that i can "unscrew the vent", do you mean the top of the air eliminator that hold the actual vent topped with the black cap? i think that part was confusing.

i can replace the whole air eliminator, the guts only, the cover with the vent and the cap.

 

D,
We're talking about 2 different things I think. The pic you showed was of an air vent into the boiler. Now it sounds like you're talking about the same type of vent on your air scoop which is most likely on your supply pipe to the system. There is nothing rebuildable on an air scoop and the vent just unscrews from the scoop if defective or some companies sell the guts but either way you must relieve the boiler pressure so why not just change the whole thing the first time.

If I read your post right the second time it sounds like you think the black cap vent on the scoop is part of the scoop but it's not. They are separate and the whole air vent, not just the top unscrews to replace if needed.

Are we on the same page or am I still missing something. If so can you just post a pic of the scoop and what you want to replace.

 

spott, i think we're good. sorry if there was any confusion

 

Why not give up on the boiler vent and put a new on at the highest in the system. Ultimately, that is where air ends up in most systems.

Without shutting down the system you can use a saddle valve as a vent or to connect an automatic one to it.

 

closing a loop on this one. i bought the same air scoop as i have installed and took it apart. took some convincing (vice+pipe wrench) to unscrew that puppy for some reason.

after that i decided to manually vent the air from the system and it went just fine. some air came out and then some water. i ended up screwing the cap tight for few days since water was slowly seeping out, but then i loosened it and was all dry afterwards.

no air in the system, nice and quiet now. and i have a spare air scoop just in case.

 

Nice way to start 2017. Happy New Year!!!