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  1. #1
    Join Date
    Mar 2009
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    232

    Default Boiler Wont Hold Water

    Last night the home boiler leaked all of its water to the basement floor. I always check the water pressure daily and open the cold water to bring it up if needed but this was very unusual. All 13-15psi was down to 0 and there was traces of water all over. Now i refilled and the pressure relief valve is dripping without the boiler even on. I recently had the valve replaced and it was working fine for the past 2 months. Any idea what happened here and what i have to do to get it back in working order?
    My advice and opinions come from hands on knowledge...and This Old House Hidden Content

  2. #2
    Join Date
    Jul 2010
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    SoCal
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    5,438

    Default Re: Boiler Wont Hold Water

    The boiler is leaking and the T&P valve is dripping? replace them. Is it still under warranty? regardless, do it ASAP, you can't afford floods in the basement.

  3. #3
    Join Date
    Mar 2009
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    232

    Default Re: Boiler Wont Hold Water

    Sorry for any confusion. I can see the water leaking from the T&P valve with a drip every few seconds. It's just odd that this morning, the boiler was at 0psi and I could see all of the water was on the floor. T&P valve was replaced recently which is why i'm confused as to why this happened all of a sudden.
    My advice and opinions come from hands on knowledge...and This Old House Hidden Content

  4. #4
    Join Date
    Feb 2010
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    1,183

    Default Re: Boiler Wont Hold Water

    Sounds like expansion tank problems. The fix depends on the type tank you have, bladder or one that needs periodic draining. If it's a bladder tank it needs replacing if the tank is suspended between the floor joists it needs draining. When the tank fails it causes the relief valve to open that can cause debris to enter the valve and prevent it from re-closing closing.

    John
    Last edited by johnjh2o; 02-12-2012 at 08:41 PM.

  5. #5
    Join Date
    Feb 2008
    Posts
    180

    Default Re: Boiler Wont Hold Water

    dcalabro:

    Yes, I agree with the others that it's probably a minor problem with one of the components & not something more serious; what is the boiler gauge reading now????

    The PRV (pressure relief valve) is designed as a safety device-----ordinarily, when cold, the boiler should read aprox 12 PSI------however, when the boiler fires up, the heated water inside expands approx 4% because water always expands when it is heated; thus, if your HW system has approx 15 gallons (typical), the volume inside the system will expand by approx 3/4 gallon----this extra water has to go somewhere or its added water volume will crack the piping, or the cast iron sections; thus, an EXPANSION TANK is part of the system, with an inner expandable neoprene bladder that will absorb the added volume; however, if the expansion tank has lost its inner bladder air charge due to an internal leak, the ET will get "waterlogged" & as the boiler continues to heat up to 180 degrees, the added water volume will open the PRV (always rated at 30 PSI) & approx 1/2 gal. will spill on the floor to relieve the increased water pressure inside the system----thus, the PRV is DOING ITS JOB of opening as it should to protect the system; thus, when the system is cold, the boiler pressure gauge needle should read approx 12 psi; when the system is hot, the gauge should read approx 20-25 psi.

    This assumes you recently replaced the the PRV with the properly rated valve of 30 psi.

    If you have a bladder-type expansion tank (usually gray steel, approx 1.5' X 1.5', saying "Extrol" or others, are always shipped from factory w/12psi of air inside the bladder) check the bottom of the ET for a bicycle-type air valve at the bottom of the ET; take the thumbnail of your thumb & press it into the air valve mechanism until you hear or feel some air escape---then immediately release your thumb---if you see any moisture on your thumb, the tank is leaking & has to be replaced; often tapping the ET with a small hammer on the top & bottom can indicate by sound if the ET is completely filled with water (defective) or 1/2 filled with air (good).

    The home improvement/home & auto/bicycle shops sell an air pressure gauge that can verify that 12 psi is present in the lower part of the ET; a hand-driven bicycle pump can restore the air to 12 psi, but, again, if you detected any moisture with your thumb, replace the ET.

    Post back to learn how, or call a service tech if you don't want to DIY.

    Post back with your test results, or report if you have an older-type 4' steel expansion tank attached to the floor joists above the boiler.

    There is a remote possibility that one or two other things are causing the PRV to trip, but check the above conditions first.
    Last edited by Dobbs; 02-12-2012 at 09:55 PM.

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