Air in heating pipes

Old 01-30-08, 11:14 AM
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Air in heating pipes


I recently tried to bleed my baseboard heating elements, but think I let air into the system instead of bleeding it out. I don't seem to be getting much hot water up to the second floor baseboards now.

I found the flow valve to add water to the system, right where the cold water pipe enters the boiler.

What is the best way to remove all the air from the pipes and get hot water flowing up to the second floor again? I have an old American Standard boiler.

Old 01-30-08, 11:32 AM
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The only way air gets in is if the water pressure is too low. As air bleeds out, water needs to be added to maintain adequate pressure.

Typically, you want a minimum of 5 psi at the highest point so in order to get that, measure the highest point above the gauge in feet, divide by 2.31 and then add 5. That or 15, whichever is greater.

Do you have bleeders at the rads or do you purge at the boiler. I won't comment on purging, I leave that to Captain Aquastat.

If bleeding, get the system good and hot, then shut off the circ(s)/system and slowly add some water to bump the pressure up to 25 to 28 psi, and then go around in order of the flow and start bleeding rads. If you get much air out of any, you may need to add more water to keep the pressure up.
Old 01-30-08, 02:50 PM
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I think Who (aka Mr. Monoflo) is referring to me ...

Scott, there should be a pressure/temperature gauge on your boiler, can you tell us what it reads ?

It sounds as though you do have low pressure, and you may indeed be sucking air in when you open bleeders on the upper level.

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