Air in the system, even after it was bled

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Old 01-11-09, 02:17 PM
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Air in the system, even after it was bled

Hello,

I keep getting air in the system. I bled the system myself, i had a plumber do it and it usually helps for a few days. After a few days i hear a little noise, in a week or two it sounds like a little creek and later like a waterfall.

The only air vent i have is on water supply side. Here is a picture

Picasa Web Albums - kilativ - heating issues

I've heard so many opinions. One plumber said i need to replace the water expansion tank. I have the old type, the one with air inside.

Another one said i need to replace this thing
Picasa Web Albums - kilativ - heating issues
I can't figure out what is the purpose of it, but i find it hard to believe it removes the air.

I did some research, i think i need an air eliminator, i asked another plumber to take a look at my system and install one. he said my system wasn't bled correctly, bled it again for $300 and in 2 weeks i hear the noises again. He claims it's impossible for the air to get in. Why would they sell air eliminators if that is the case.

I can't pay $300 for every new opinion and not get any results.

Any suggestions? Should i install something like Spirovent air eliminator? Where is the best to install one?

Thank you in advance.

v
 
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Old 01-11-09, 03:50 PM
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Originally Posted by kilativ View Post
Another one said i need to replace this thing
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I can't figure out what is the purpose of it, but i find it hard to believe it removes the air.
v
The green fitting is to remove air and direct it to the expansion tank. Bell & Gossett calls their version of that component an Airtrol fitting. With a conventional expansion tank, it is customary to use such a fitting instead of an automatic vent to atmosphere, which would ultimately deplete the air from the expansion tank.
Doug
 
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Old 01-11-09, 04:33 PM
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Thanks for clarifying this Doug. i guess i was wrong, it does remove the air.

Does it mean mean the airtrol fitting is bad than in my system? This would be the only way to get the air into the system. From the expansion tank.

Sounds like i have two options. To replace the Airtrol fitting or to get a bladder type expansion tank and an automatic vent. Right?
 
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Old 01-11-09, 04:46 PM
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Just to restate and reinforce what Doug said...

You do NOT want to use an air VENT of any kind on a system that uses a conventional steel compression tank.

Unless that expansion tank is leaking, you do NOT need to replace it. It _may_ be piped incorrectly... the pipes leading up to that tank must slope upward at least 1/4" per foot all the way to the tank. 1/2" pipe is OK... but 3/4" pipe is better. The air in the system needs to find it's way to that expansion tank.

I'm not familiar with them old fittings... does the pipe to the expansion tank connect to the backside and can't be seen in the photo? It looks like a flow check valve to me...

I'd like to see more pictures from a further distance so we can see what's what.
 
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Old 01-11-09, 05:05 PM
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Even if that old fitting is intended to direct air to the tank, it probably doesn't do a real good job of it. Probably works fine as a check valve though.

If you wanted to improve the air removal of your system, you could install an air separator and pipe the old tank to it... here's one that will work with EITHER your old tank, OR a bladder tank with a vent on top.

/BG air separator

Leave the green thing... install this after it... pipe the old tank to the top of it... plug the hole on the side of the green thing... plug the hole on the bottom of the IAS.

[edit: I just looked at the pics again... perhaps a better place to install the separator would be on that horizontal section of pipe at the top of the boiler...]
 
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Old 01-11-09, 05:44 PM
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Originally Posted by NJ Trooper View Post
If you wanted to improve the air removal of your system, you could install an air separator and pipe the old tank to it... here's one that will work with EITHER your old tank, OR a bladder tank with a vent on top.

/BG air separator

Leave the green thing... install this after it... pipe the old tank to the top of it... plug the hole on the side of the green thing... plug the hole on the bottom of the IAS.

[edit: I just looked at the pics again... perhaps a better place to install the separator would be on that horizontal section of pipe at the top of the boiler...]
OK, Mr. Trooper. I was just getting ready to post something about this, and then encountered your edit.

I do like the idea of installing the B&G air separator, but I'm not sure about leaving in the "green thing." If the green thing is clogged or otherwise not functioning, etc., then it seems that it might be better to ditch it altogether.

My ~60-year-old hot-water boiler has a B&G conventional expansion tank, a B&G Airtrol tank fitting, and a B&G Airtrol boiler fitting (no longer sold - use your suggested B&G air separator instead) - the whole system works great.

I would like to see a pix of where the pipe connects to the expansion tank. I would prefer to see a B&G Airtrol tank fitting there (they are still sold).

B&G worked out all those air-removal details well over a half-century ago, and I respect them. Not the cheapest, by far, but very reliable, U.S. made. Hydronics people are still trying to elbow their way into B&G's Little Red Schoolhouse (free, but by invitation only) - wish I could go!
Doug
 
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Old 01-11-09, 06:13 PM
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wow guys, why those plumbers who claim to have 25 years of experience don't know any of that?!

I got more more pictures, meanwhile i'll try digest your responses.

Thanks again

Air fitter from the other side (where expansion tank connects)
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expansion tank connection (i used a level and if there is a slope it's very small. Probably 1/8" of an inch per foot, definitely less than 1/4"

Picasa Web Albums - kilativ - heating issues
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v
 
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Old 01-11-09, 06:54 PM
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The slope should be greater, I think.

I would prefer to see a B&G Airtrol tank fitting at the tank. But, I think the main improvement would be the B&G air separator, properly installed.
Doug
 
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Old 01-11-09, 07:05 PM
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Originally Posted by NJ Trooper View Post
Even if that old fitting is intended to direct air to the tank, it probably doesn't do a real good job of it. Probably works fine as a check valve though.

If you wanted to improve the air removal of your system, you could install an air separator and pipe the old tank to it... here's one that will work with EITHER your old tank, OR a bladder tank with a vent on top.

/BG air separator

Leave the green thing... install this after it... pipe the old tank to the top of it... plug the hole on the side of the green thing... plug the hole on the bottom of the IAS.

[edit: I just looked at the pics again... perhaps a better place to install the separator would be on that horizontal section of pipe at the top of the boiler...]
thanks! i am still trying to understand what that means. where to install it. after the green thing on the main loop? or on the pipe to the expansion tank? What does "plug the hole on the side of the green thing" mean?

The top should be connected to the expansion tank using a t-fitting?

I am sorry i am slow to pick this up. Plumbing is new to me.

thanks again
 
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Old 01-11-09, 07:34 PM
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Now that I see more of the system, and the zone valves... I'm gonna say that you probably don't need 'Old Greenie' too. The zone valves should stop any issues with 'gravity flow' that the check valve was there to stop.

The IAS we pointed to at the B&G site needs to be installed horizontally. So _some_ repiping will be necessary.

My original suggestion to 'plug the hole in the side' would have been because the connection to the tank would be removed from there. Ya gotta close that hole up of course.

New piping, 3/4" in size from the compression tank to the new IAS, where ever it gets installed, with the proper slope to allow the air to get back to the tank.

It looks like it might be pretty easy to remove the vertical pipe that Greenie is mounted on, and replace it with something a bit shorter.

Then, elbow to horizontal, install the IAS, and reconnect the zones to the outlet of the IAS.

There's another port on the bottom of the IAS that would need a plug also.

However... if you do that, you do have the option of ditching the old tank, hanging a bladder tank from the IAS, and installing an auto air vent on top...

Where is the circulator located? I'm gonna look at the pics again...
 
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Old 01-11-09, 07:42 PM
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You can see the circulator on the first picture on the bottom
Picasa Web Albums - kilativ - heating issues

I have a feeling this house was one-zone at some point.


I think i understand what you are saying now. I'll try to draw the diagram and post it here, just to make sure i got. I am thinking of doing this in the summer, other than noise the system is working ok.

thanks again.
 
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Old 01-11-09, 07:45 PM
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OK, I looked... there's the circ on the return ... but ya know what I think is really odd? The fact that you have what appears to be (pics can lie...) a single piece of 3/4" pipe running into the pump.

There was obviously some retro-fitting done a while ago.

What's up with that piece of fin-tube baseboard without a cabinet on the ceiling? That's pretty weird too...

And that one zone valve... comes out, turns around and goes back and down ...

I think to figure this one out, one would have to be there to see it. And the reason the other guys 'didn't know this' ? Answer is simple... they don't care. $300 for nothing... why would they want to work for their money?
 
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Old 01-11-09, 07:58 PM
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just measured it, it is less than 1 inch in diameter. It's the same size from the moment it leaves that old greenie thing, throughout the house and to the circulator.

This house was expanded twice, so a lot of strange things were done.

the first zone that you say turns around and goes down, i think they just didn't have enough space to put the valve in, so the did a u-turn thing.

the baseboard on top is a mystery to me too.
 
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Old 01-11-09, 08:21 PM
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The 'old green thingie' is a Thrush Flow Control Valve. It prevents gravity flow through the system along with separating air and returning it to the tank. The pipe out of the far side should have a slight upward slope to the expansion tank. This is to allow air to bleed back to the tank.

The air vent on the other line should not be installed. That will cause the expansion tank to become water logged as air is vented from the system.

Seems as through several changes have been made to the system that are not in sync with each other. Hence the problems.

Al.
 
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Old 01-12-09, 09:12 AM
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You might be able to do a world of good just by increasing the slope of the pipe to the expansion tank - during the first warm spell this winter.

That might be a pretty easy job. See the nipple between the tee and the expansion tank connection? That nipple might be, say, 2" long? Replace it with a close nipple, and that would give you more slope in the pipe.

Then, you'd have the rest of the winter to see how much good it did.
Doug
 
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Old 01-12-09, 05:39 PM
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Doug's got a good idea I think... why not give that a try? Certainly the easiest and cheapest... then in the spring, if it didn't work out as you liked, do some re-piping then, when you don't need the heat.

[edit: just looked at the pics again... I bet it's gonna be a beotch to get that old nip outta there...]

Reason I mentioned that the 3/4" into the pump is weird... that size pipe is generally good for only about 40K BTU at a reasonable flow rate. Any time you join two pipes together, you should step up in size ... two 1/2" will go to a 3/4", two 3/4" will go to 1", two 1" will ALMOST go to 1-1/4"... etc ... so where the two zones join on the supply and return should be at least 1" pipe.

I'm willing to bet that boiler is WAY oversized for your needs...
 
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Old 01-12-09, 06:05 PM
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Does this mean i need to drain the compression tank? Plumbing is so new to me i doubt i can do it myself. I can do electrical work, carpentry, but somehow plumbing always scared me.

I think in the spring i'll get the BG air separator, the bladder type expansion tank and an air valve and hire somebody to install it.

Or may i should give it a try myself.

you are right about pipes. it doesn't step up in size when both zones join on return. Knowing the basics of physics it doesn't make any sense as a lot of things in this house.
 
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Old 01-12-09, 06:29 PM
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If you're nervous about plumbing work, I would wait 'til spring, and get somebody to do it. Sure as I sit here, as simple as the job looks, there will be a problem crop up.

Yes, you would have to drain the system.
Doug
 
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Old 01-12-09, 06:47 PM
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just chatted with the plumber who bled the system the last time. He is convinced that it's not the compression tank as it would get waterlogged. But he is suggesting to install a spirovent air eliminator and a bladder type expansion, which is essentially the same solution as you guys suggested.
 
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Old 01-13-09, 08:53 AM
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Originally Posted by kilativ View Post
just chatted with the plumber who bled the system the last time. He is convinced that it's not the compression tank as it would get waterlogged. But he is suggesting to install a spirovent air eliminator and a bladder type expansion, which is essentially the same solution as you guys suggested.
No, I don't think that was specifically recommended here.

I don't think "it's" the expansion tank either. But it may be the failure of the green fitting to effectively remove air and direct it to the expansion tank. If that, in fact, is the problem, replacing the tank with a bladder type is probably not the least expensive solution.

If you keep bleeding air out of the system, and little or no air is directed into the expansion tank, then, yes, the tank will eventually become waterlogged.

There are millions of conventional expansion tanks out there that work fine, including mine. Does your plumber think they should all be replaced?
Doug
 
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Old 01-13-09, 09:06 AM
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I am not really agreeing with the plumber, just kind of makes sense that by removing the only part of the system that has air would help.

i don't trust him 100% because he can't explain why the air is in the system.

I'll try to make it through the winter and then experiment and learn plumbing.

If i install BG Air Separator why do i need the green thing at all?
 
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Old 01-13-09, 12:34 PM
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I am not really agreeing with the plumber, just kind of makes sense that by removing the only part of the system that has air would help.
The expansion tank is supposed to have air in it. If, in fact, the tank is losing air to the system, it is likely because the line isn't properly sloped or that the green device isn't doing its job for some other reason.

If i install BG Air Separator why do i need the green thing at all?
As "Oldboiler" explained, the green device serves two purposes: (1) as an air eliminator to direct air into the expansion tank, and (2) as a flo-control valve to prevent gravity flow when the circulator is not running.

Function (1) is evidently not working, possibly because the line to the expansion tank isn't properly sloped. Replacing it with the B&G air separator recommended by "NJ Trooper" might help, but may not help if you don't correct the piping slope too.

Function (2) may be working. But that function won't be served by the B&G air separator. For preventing gravity flow, you'd need to somehow leave the green device connected in the main supply line or install a new flo-control valve such as manufactured by B&G or Taco.
Doug
 
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Old 01-13-09, 12:44 PM
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Thank you for the explanation?

what is "gravity flow"?
 
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Old 01-13-09, 12:47 PM
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Originally Posted by kilativ View Post
Thank you for the explanation?

what is "gravity flow"?
Warm water that circulates by gravity when the circulator isn't running and the thermostat isn't calling for heat.
Doug
 
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Old 01-13-09, 06:17 PM
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Function (2) may be working. But that function won't be served by the B&G air separator. For preventing gravity flow, you'd need to somehow leave the green device connected in the main supply line or install a new flo-control valve such as manufactured by B&G or Taco.
Shouldn't/wouldn't the zone valves prevent gravity flow?

Wanna know what I would do if it was my system? No? too bad, I'm gonna tellya anyway!

I would rip out a lot of the piping and properly pipe the supply and returns with the correct size manifolds. I would at the same time set the pump and expansion tank up so that the pump was pumping away from the tank. This would solve the air problems... and the system wouldn't be 'choked' by running two zones into 3/4" pipe.

kila, think about it ... that system is pretty 'organic'... and it really wouldn't hurt to 'consolidate' the changes that were made over the years. In the spring time of course...
 
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Old 01-13-09, 06:23 PM
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Originally Posted by NJ Trooper View Post
Shouldn't/wouldn't the zone valves prevent gravity flow?
Duhh - OK. Then just replace the green thing with a B&G air remover and increase the slope of the pipe. Couple of hours of labor.

But, yes, that system needs to be thoroughly gone over by an experienced hot-water boiler person. Not a lot of cost - mainly piping changes. It seems like a number of people may have had their fingers in this system over the years?
Doug
 
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Old 01-13-09, 06:41 PM
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Thank you guys for all the knowledge. I am glad i found this website.
 
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Old 04-04-09, 05:20 PM
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Ready to do the work

Hi, i am resurrecting the old topic. Now that the heating season is almost over i want to get this over with. I am thinking of replacing the expansion tank with the new bladder type one and installing an air valve. This way whatever the reason is for the air i'll get rid of it.

What size of the expansion tank do i need for a 2 zone, 2400 sq ft house?

Thanks
 
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Old 04-05-09, 09:02 AM
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Hey Kila, Happy Spring!

I don't think that simply replacing the tank is going to solve all your problems...

I haven't looked back at your pics or refreshed my memory of your system, but in order to properly size the tank some estimate of the amount of water in the system has to be done. The size that is most commonly seen is a "30"... chances are this will do it for you... but don't take that as 'gospel'...

There's absolutely nothing wrong with keeping your old tank. If it's piped properly it will do every bit as good a job as a bladder tank.
 
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Old 04-14-09, 05:03 PM
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Sleeper...

in case you can't find it, I moved your 'hijack' to it's own thread:

Air in system, gurgling pipes, etc
 
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