Can't seem to get all the air out

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  #1  
Old 10-18-18, 06:51 AM
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Can't seem to get all the air out

I needed to drain some water out of my second floor zone and for the life of me I can't seem to purge all the air out of that zone now. I can hear the water swooshing through the lines, then it will stop in that section and then a few minutes later the water swooshing is back. I have purged the system 3-4 times now with this last time running at least 30 gallons through the loop just to make sure the water had plenty of time to make it around. I closed the shut off valves, opened the drains into a bucket, opened the zone valve manually then opened up the water feed bypass and let it run. I am getting heat to that area but there is definitely still air in the system. Do you think since it is my second floor that it is not filling the pipes fully before it come back down the return pipe? I even added a bleeder valve last night but when I manually opened it I didn't hear too much air coming out. Any help would be appreciated!!

Thanks!
 
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Old 10-18-18, 08:53 AM
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What is your system pressure?
 
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Old 10-18-18, 08:55 AM
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do you mean what is on the gauge? It says around 11lbs
 
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Old 10-18-18, 09:06 AM
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11 psi is marginal for a 2-story house. Temporarily, jack up the system pressure to 25 psi, and try purging again.
 
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Old 10-18-18, 09:08 AM
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I always let the system rest for several minutes after a heating cycle and then go to the highest point in the loop to get the air bubbles that may have accumulated. Plan to repeat 2 or 3 times, getting less and less air in each successive bleed.

New water brings in a lot of air with it,

Haven't had a noisy bubble now for years.
 
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Old 10-18-18, 09:21 AM
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thanks for the tips!

I am getting a lot of air out of the vent that is above the expansion tank but got nothing from the vent that installed last night at what I think is the highest point of the loop.
 
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Old 10-18-18, 09:36 AM
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I think you may have deflated the air side of the expansion tank bladder! Post some photos so we can understand exactly what you are doing.
 
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Old 10-18-18, 10:26 AM
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s,
Your auto feed valve comes factory set at 12PSI so since fresh water brings air with it you are just creating a cycle of removing the air through bleeding then reintroducing the air with fresh water.

With the procedure you used get your boiler pressure up to at least 25 or as close to 30 PSI without the relief going off.

Bleed the zone never letting the pressure drop below 22-25 PSI. When all the air is removed close the feed and the drawoff.

You should have at least the 22-25 PSI in the system. Now you can drain off a little water until you get down to your operating pressure which should be around 16-18 PSI.

You want to end up with a higher pressure than your feed valve is set at so that when you're done bleeding it will not be able to introduce fresh water into your system bringing more air.

I would close the cap on the vent you just installed to stop any air from getting sucked in when the pump comes on. You already know it's not helping.

This bleeding should all be done with your boiler and pump off. You want natural pressure, not increased by pump.

When all done make sure all valves are open to the system and turn on boiler to test for proper operation.

As long as you maintain that pressure you shouldn't have any more air problems if the system is not opened.

Hope this helps a little.
 
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Old 10-18-18, 10:30 AM
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For some reason the vent was screwed down on the vent above the bladder and when I when I opened it i got a few seconds of air out of it. How would I know if my bladder is bad? It sounds dense on top and slightly hollower on the bottom when I knock on it.
 
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Old 10-18-18, 10:49 AM
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By the looks of that vent it was closed because it leaked. You can close it again if it is leaking until it can be changed.

If your tank has a hollow sound on the bottom that means you at least have an air charge in your bladder.

To find out the PSI of that charge there is a RED CAP on the bottom of the tank that unscrews revealing a Schrader valve. With an air pressure gauge check the charge. It should be at least 12-15 PSI.
 
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Old 10-18-18, 11:19 AM
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Awesome! I will hopefully get a chance to do this tonight when I get home and give you my results!

Thanks a bunch!
 
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Old 10-19-18, 09:26 AM
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You should not bleed the expansion tank, except very briefly on expansion tanks hanging down.

Otherwise you may need to go through a complex recharging procedure.

The expansion tank should be preset to the expected cold system pressure (12 or so PSI) using a tire gauge after the autofeed is shut off and so much water has been let out so the system pressure gauge reads zero. If the system gauge rises while you are adding air, then stop every so often and let more water out until the system drops back to zero before continuing. Then you need to refill the system up to the 25 or so PSI needed to do the bleeding with.

Then bleed the system via the radiator bleed valves or other bleed valves. Systems with baseboard radiators will usually hold only small pockets of air requiring going through them several times over several days to get most of the air out.

As you bleed the system, you may need to add more water to get back up to 25 PSI. Otherwise opening a bleed valve may suck more air in rather than let air out.
 
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Old 10-19-18, 10:41 AM
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this might be a dumb question to a pro but since i am not I am going to ask. How do i maintain the 25lbs of pressure in order to bleed the zone? usually as soon as I open the drain for that zone it goes down to practically zero. Do i just open up the drain a little bit to maintain pressure?
 
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Old 10-19-18, 11:21 AM
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There are no dumb questions unless I say so as a defensive response because I don't know the answer but in this case I think we're safe.

You open up your lever on your feed valve so the boiler fast fills as your bleeding.

Lift the lever on your feed valve which bypasses the auto setting of the valve. When you get to 25-28 PSI open your drawoff to start the bleeding. Keep the lever up feeding the water to maintain pressure.

If it feeds to fast so that it fills faster than it drains shut the lever periodically so the relief valve doesn't go off. If you have low water pressure where you are and it drains faster than it fills it will take you longer but fill until the high pressure is achieved and bleed only until the pressure drops to about 22 or 20 PSI then shut your drain and repressurize to 28.

You could try bleeding slower if that helps by not opening the drawoff all the way.
 
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Old 10-21-18, 10:00 AM
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Thanks to everyone, I now have no air in my system. Just had to crank up the pressure a little more just like you said!!!
 
  #16  
Old 10-21-18, 10:29 AM
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S,
Thank you for the update.
 
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