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How to Bleed a Boiler

reghireghi Member Posts: 17
I have a gas boiler with 2 zones, 2 circulator pumps and 2 relays. See attached diagram

When I bleed the system this is what I basically do. I turn all the shut-off valves off, except for line going out to the baseboards of the zone I am going to bleed, disengage the fill valve pressure regulator and then I open the drain petcock above the circulator pump and let it run for about a minute or two and then repeat for the second zone. However, when I do the above the tridicator gauge shows 0 psi pressure.

Is the way I am bleeding the system correct?


  • unclejohnunclejohn Member Posts: 1,544
    edited December 2015
    You most likely need to open one of the valves by the pump. I don't know where your fill valve is or your bleed drain. Can you show them on the drawing. Ok I see your drain I thought it was the gauge. What do you mean by disengage the fill valve? You need to open the fill valve when you bleed.
  • reghireghi Member Posts: 17
    I open the fill valve, however, the water is not coming in fast enough and I I lose pressure.

    I am thinking that the fill valve is no good. I will call bell and gossett tomorrow and see if I can adjust the valve (its an FB-38)
  • unclejohnunclejohn Member Posts: 1,544
    Your better off just replacing it. replace the backflow while your at it.
  • reghireghi Member Posts: 17
    Called Bell and Gossett tech department and they told me that the fill valve might be clogged. I will check the strainer this weekend and hopefully this solves it. According to B&G it is very rare for the fill valve to fail.
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