Fixed One Lagging Radiator - New Problem with Pressure

Old 10-24-07, 11:58 AM
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Fixed One Lagging Radiator - New Problem with Pressure

Suddenly, out of nowhere, the one lagging baseboard heater in my room has heat. I have been bleeding a little water every day, in hopes to move the bubble. It finally got cold the last couple of days here, and the boiler has been running more frequently, so I suppose the air bubble could have been pushed somewhere else. Who knows.

But, when I went down to check out the pressure, it was at about 29psi. I have been watching this like a hawk, given that I've never lived in a house with a boiler. We've been keeping the pressure at about 16-17psi while the boiler isn't running (the valve that reduces the pressure isn't working, and I was told that until it was warmer and we can risk having to shut the boiler down, manual maintenance of pressure would be acceptable.

From my understanding, this would point to a lack of sufficient air space in the expansion tank. The procedure for fixing I believe goes something like attaching a hose to the drain valve and draining some water out. The problem is that I'm not sure how much to drain out and given the nature of it, I'm not even sure if there is a window to see how much is in there. (Picture below).

Any tips, pointers, etc would be appreciated. This forum has already helped me get heat into my bedroom (and avoid a costly visit from the boiler guy) for which I am very grateful!

Old 10-24-07, 01:55 PM
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Yes, you need to drain the expansion tank.

I detest those Bell & Gossett AirTrol fittings (the red fitting that connects the tank to the boiler) and I have never been able to properly drain an expansion tank with them. The B&G instructions tell us that when once properly filled they need no more service.


You will have to cool down your system to about 100 degrees, close off the water feed, open the boiler drain and open the little vent valve on the bottom of the AirTrol fitting. Let it drain until the AirTrol vent is no longer gurgling and then close the vent and the boiler drain. Open the water feed valve and let the pressure climb to the 12 psi setting of the feed regulator and then fire up again.

I strongly urge you to replace that tank with a diaphragm type tank next summer.
Old 10-24-07, 04:02 PM
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Draining Tank

I too detest those AirTrol devices. They will leak air but not water.

I'd like to expand on Furd's draining procedure a bit & hopefully save you some grief:
There should be a shut off valve between the tank & the boiler. Close it.
Attach a hose to the hose bib of the tank & put the other end in a bucket or run to a sump pump.
Open the hose bib & allow water to run as long as it will.
Open the air valve on the AirTrol. If I remember right, you'll need a 3/8" wrench. Having a piece of hose which will fit snuggly over the air vent will make it easier to force (blow) air into the tank since those AirTrol's often won't start drawing air on their own.
Drain the tank completely.
Close the AirTrol & hose bib.
Slowly open the valve between the tank & the boiler while trying to maintain 12-15# on the boiler gauge.
Maintaining this pressure should reduce the chances of air getting into the rest of the system.
Old 10-24-07, 04:31 PM
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Hey Schteve, that bubble could well have moved _because_ of the increased pressure ! Good deal...

Sometimes using a short hose on the drain bib makes it easier to get all the water out. The reason you need to blow INTO the tank is because it will be 'vacuum locked', same principle as when you put your finger over a straw and pull it out of the glass, the soda/water/whiskey stays in the straw.

BEWARE that water will be schtinky and naschty ... don't get a face full !

You can even use a small air compressor to blow into the tank, just don't go crazy with the pressure, a couple ten psi is more than enough.

Have fun!
Old 10-24-07, 05:30 PM
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Best thing I ever did on my old system was rip my conventional tank out. I hung a bladder tank off the tee that fed the old tank and where the water feed came in I ran a vertical riser off a tee and stuck on autovent on it. Voilą!

Saved my twice a year drain the tank ritual!
Old 10-25-07, 07:06 AM
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air cushion tank

The best advice is to change to an new bladder type air cushion tank and if you can do it yourself it wil cost you no more than $100.
An Amtrol 30 is suitable for most small/medium sized systems and can be had for about $50.

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