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no shut off between boiler and air eliminator

Hi, I'm trying to purge my system of air. It was built in the mid-70s, and for whatever reason, there are no purge valves on the baseboards. Apparently no one has thought to change this prior to us moving in. It's a three zone system, and there are no shut off valves for each zone. So, my questions are:
1. do I engage the motor to open up each zone to purge?
2. there doesn't seem to be any air popping out of the drain when I bleed. How long do I need to bleed?
3. Since there is no shut off between the air eliminator (supervent) and the boiler, will there be pressure if I attempt to change the head, or clean it?



  • JohnNYJohnNY Posts: 2,040Member
    Pictures please.
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    John is a professional Master Plumber by trade, licensed by The Department of Buildings of The City of New York, but travels regularly to out-of-state clients for consulting work.
  • EBEBRATT-EdEBEBRATT-Ed Posts: 4,338Member
    Most of the older jobs were pretty naked when it comes to valves, they were considered expensive back then. They still are not cheap but labor prices are high so valves are more common now and really make for much better serviceability.

    Even putting in two valves one on the main supply and one on the main return allow for working on any boiler component without draining the entire system
  • HomerJSmithHomerJSmith Posts: 477Member
    edited November 10
    If it is Honeywell zone valves, there is a lever under the box that allows you to manually open each valve as with many other makes of valves. It has a catch to hold the lever in the open position. You don't have to motorize the valve although you can.

    What do you mean "any air popping out of the drain when I bleed"? and "will there be pressure if I attempt to change the head, or clean it?" If you are talking about the Honeywell Supervent and taking it apart, most likely, yes, especially if it is a two story house. Drain the boiler first.

    To purge the air out of a sys you need a minimum of 2 hose bibbs in the right places. Using a fill valve to push the air out of a sys is futile unless it has a street pressure loop or a fast fill lever.

    I have used garden hose connected to a water heater to purge a boiler, but you have to be careful of blowing the pressure relief valve (PRV). With a boiler that old I would replace the bibb gasket or boiler bibb also replace the PRV. I would check the expansion tank for the proper air charge if a diaphragm tank before refilling the sys.

    You need high pressure to purge a sys, so street pressure off the w/h will give you that. Flush the sys and run the hose until no air bubbles come out and the hose doesn't sputter. Do one zone at a time, shut it off and go to the next zone. When the water runs clean open all the zones and run the water thru until you have a steady stream with no air bubbles. I place the hose end in a five gal bucket to observe any air bubbles.

    Hope this helps.
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