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Thread: Boiler fill valve not filling

  1. #1
    DIY Senior Member rockycmt's Avatar
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    Default Boiler fill valve not filling

    My fill valve is not filling. I adjusted the screw on top and I do not see pressure building in the boiler tank. Last fall I had a similar issue. Then I adjusted the screw a 1/2 turn and it adjusted pressure correctly. This year the screw seems to do nothing. I lowered it and raised it wil no affect. Boiled still only has 2psi. Does this unit fail in this way? There also seems to be a cleanout on the bottom. Is this another option to free the blockage? Or just replace?

  2. #2
    Janitorial Technician nestork's Avatar
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    Most likely the problem is a clogged filtration screen on the valve.

    If your pressure reducing valve kinda looks like this:



    Then one of the openings on the bottom of the valve will be to remove the filtration screen for cleaning, and the other will be to access the internal parts of the valve, like this:



    where that "cylinder" on the left is a cylindrical wire mesh screen to filter out any dirt or crap from getting into your heating system.

    It's very possible that your filtration screen is just clogged.

    You can usually purchase replacement filtration screens from the manufacturer, and I know Watts used to make an overhaul kit available as a part for their pressure reducing valves.

    If it turns out that the problem isn't just a clogged filtration screen, and you opt for replacing the valve, a real good way to set it up is to have a pressure gauge (first) and a ball valve (second) within a foot or two downstream of your pressure reducing valve. That way, you can close the ball valve and tighten the pressure adjusting screw. Because of the tiny amount of volume between the PRV and the ball valve that has to be pressurized, the pressure showing on the gauge will respond immediately as you turn the adjusting screw. When the gauge reads the pressure you want, tighten the locking nut on the adjusting screw and open the ball valve. The PRV will then fill your whole system with water until it reaches that same pressure.

    The way to tell what pressure you want to see showing on your pressure gauge is to guestimate the difference in elevation between the highest point in the heating system and the pressure gauge. Multiply that difference in elevation by 0.4333 psi per foot. (See PS below.) If the number you get is anything less than 12 psi, use 12 psi. You need that much pressure to prevent cavitation from occuring on the impeller(s) of your water circulating pump(s).

    PS: The reason why the water gradient is 0.4333 is because water weighs 62.4 pounds per cubic foot. So the pressure at the bottom of a 1 cubic foot aquarium would be 62.4 pounds divided by 144 square inches, or 0.43333 pounds per square inch. And, for every foot in height you add to that aquarium, the weight of the water increases by 62.4 pounds, but the area of the bottom remains the same, so the pressure on the bottom will increase by another 0.4333 psi.
    Last edited by nestork; 10-08-2012 at 07:41 PM.

  3. #3
    DIY Senior Member rockycmt's Avatar
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    These are pics of my valve. It looks a little simpler than your pic. I have 2 pressure gauges on the reduced size of the valve. both read 2psi so i am confident the valve is not releasing water to the system.


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  4. #4
    In the Trades Tom Sawyer's Avatar
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    It has outlived it's usefulness. Replace it. There is a screen inside it and it probably is plugged but usually the spring and diaphragm are bad too.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    DIY Senior Member rockycmt's Avatar
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    I agree, I will replace it. It should be an easy swap out with the union on the right side. Does anyone know this model? I would like to get the same size unit with the same clearences so I do not need to change any piping.

  6. #6
    DIY Senior Member wjcandee's Avatar
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    Maybe you don't need the same brand if you can find one in a similar size and shape like this one at Grainger might be:

    http://www.grainger.com/Grainger/BEL...FA3?Pid=search

    Of course, you'd have to measure, but they only have 163 different ones so you should be able to find a match at any major supply house. At mine, I usually measure and bring a picture with me and a good plumbing supply nearby can usually tell me what I need from the picture.

  7. #7
    In the Trades Tom Sawyer's Avatar
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    I would replace it with a Watts S1156F/9D combination because you need a backflow preventer too.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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    Janitorial Technician nestork's Avatar
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    If it wuz me, I'd see if I could get an overhaul kit for that valve and just repair it. You'll get a new screen and you can keep your old screen as a spare.

    If you want to start replacing the valve, see if you can fit a pressure gauge and shut off valve into the line downstream of the PRV to make adjusting the pressure quick, easy and accurate.

  9. #9
    DIY Senior Member rockycmt's Avatar
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    Strange thing happened last night. I tightened the adjustment screw all the way. Water did not flow. = bad unit. I go to parts store and get a new unit. I figure I will install it this weekend. (I have time before I have to use my heat) I am sitting on the couch and I hear a loud hum. I went down to check it and the spring in the bad unit released. wated started to flow. Obviously the unit is all bad inside. boiler got 20psi. I dialed back the scrw and released some pressure down to 12psi. Plan to change out unit still.

  10. #10
    Janitorial Technician nestork's Avatar
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    It might not be a bad PRV. It might be possessed.

    Maybe see how much a plumber would charge to change it and compare that with what a priest would charge to do an exorcism.

  11. #11
    In the Trades Tom Sawyer's Avatar
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    Quote Originally Posted by nestork View Post
    If it wuz me, I'd see if I could get an overhaul kit for that valve and just repair it. You'll get a new screen and you can keep your old screen as a spare.

    If you want to start replacing the valve, see if you can fit a pressure gauge and shut off valve into the line downstream of the PRV to make adjusting the pressure quick, easy and accurate.
    If you could find one which I doubt, the overhaul kit would cost more than a new valve. There is no need to install another pressure gauge, there is already one on the boiler and there really is no adjusting. They come set for 12lbs and unless you have a 6 story house there is never a need to exceed that.
    [B]No, plumbing ain't rocket science. Unlike rocket science, plumbing requires a license[B]

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