Installed Hot Water Heater blow-off valve still leaking

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by harleysilo, Jan 11, 2007.

  1. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    Hi folks, I am a DIY'er, I've installed at least 50 blow-off valves in the past when I was a maintenance man for apts. I've never had this happen. My Hot water heater, located in basement, has been dripping through the blow-off valve for some time now (months). The valve is piped to outside the house via 3/4 copper. So I remove everything, install new valve, turn water back on, flush all air out of sytem and within minutes new valve is allowing water to drip (o.k. more like 1 gallon in 5 mins.). It's 10:00 last night so I hung up my torch and will deal with it tonight.

    We have high water pressure at this house, a cheapo presure guage on the closest outside facuet says 140 psi but that can't be right. I adjusted the Presure regulator all the way out, now terrbile flow at faucets, but still the valve is leaking on the HT water heater.

    Could the new one just be faulty?
  2. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    You need to do the following Turn off the water to the water heater. See if the leak stops. Check the pressure at a hose bib with the water off to the heater. If it is still 140 or so you have a failed pressure reducing valve. A pressure reducing valve creates a closed system and you need an expansion tank installed somewhere on the cold line between the water heater and main shutoff valve as well as replacing the PRV. Most expansion tanks are located somewhere over the heater on the cold side betwee the tank and tank shutoff.
  3. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    Currently there is an expansion tank installed 1 foot above the water heater, on the cold side.

    When I shut off water to the heater, the blow off valve promptly stops leaking. If I turn on hot water somewhere in the house the blow off valve stops leaking.
    However, even when the tank was cold last night, once the tank filled up it started leaking, adjusting the PRV did not affect the leak, but it did affect pressure at the faucets througout the house. Can I presume the PRV works then? And that the Presure relief valve is faulty?
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,262
    Location:
    New England
    From reading here, one of the failure modes of a PRV is that it doesn't hold the pressure - after awhile, it creeps back up. While water is being drawn, it may reduce things, but once you stop that, it goes up. Now, yours may not be bad. But, your expansion tank could be. Take the cap off of the expansion tank and see if it lets out any water. If not, rap on it and see if it is full of water (it shouldn't be). To check the pressure in the tank, you need to shut off the water and open a faucet to relieve the water pressure, then check it with a tire pressure gauge. It should be at approximately the water pressure after the PRV so that it can accept water only when the heater is on - this will keep the maximum volume available for the tank and keep the bladder at a fairly neutral position which should extend the life since it shouldn't have to flex much under normal circumstances.

    Sometimes, when the pressure is that high, it has been suggested to put two PRV's in series, so that neither one has to contend with the full pressure. I don't know if the 140# qualifies, but it might. You might want to check the specs on the PRV you have to see what the recommended maximum delta pressure is.
  5. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    Interesting. The expansion tank did have water in it, not sure if it was full, but it had a lot of water. Here is how it is installed.

    [​IMG]

    [​IMG]
  6. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    o.k. so some searching, you guys are too nice you didn't even tell me to "Use the search Noob", has revealed my problem to be fairly common.

    I guess I didn't actually understand what a Expansion tank does, or that it is full of AIR under pressure. So on my way home I guess I'll pick up an expansion tank, and new PRV, and a 6 pack and Get er done.

    Question, so if the Expansion tank doesn't have say 60 psi, i should pump it up? Can I use my compressor or do I have to use hand pump?

    Internally, within the expansion tank, is their a valve of sorts that keeps water out?
  7. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    The tank has a baloon in it with air pressure on one side, the water expands into the baloon when it exceeds the air pressure. The tanks come pre charged. When you get the tank open the box and read the instructions and air pressure specs.
  8. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA
    You should match the expansion tank pressure to to corrected PRV setting (55 to 80 psi). I believe you have a bad PRV, which probably caused the expansion tank to fail.

    When adjusting the PRV, your adjustmens should consider the elevation of the highest fixture compared to the place where you take the pressure reading. There will be a .5 psi drop for every foot of elevation. Not important in most cases, but in some of the tall 3 story homes it can be.
  9. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    O.K. so I got a new expansion tank, installed it, it worked at full pressure when the tank was cold, but then when I turned the tank on and whatched the pressure rise to 165ish it of course started leaking again.

    I did check the tank presure it was around 60psi, i mistakely was checking the expansion tank pressure and thought oh they are the same good. So I didn't add any to the factory preset of 35psi.

    So I guess tonight I need to
    1) Drain hot water heater
    2) fill with cold water and leave water valve open
    3)check tank psi
    4)connect hose to bottom of hot water heater and drain some water
    5) check expansion tank pressure, should be 35psi
    6) pump expansion tank up to match cold water psi of probably 60ish
    7)fill water heater and turn on hope and pray

    So if that doesn't work, then I must assume I have too much "Pressure" period, and must turn down PRV say a turn or two, then start back at #1

    Sound right to you all?

    Pics, why not right?
    [​IMG]
    [​IMG]
    [​IMG]

    Yeah I can't soder, i don't even know how to spell it right
    Yeah, i bought the wrong female connector
    yeah I can't soder, but hay, i learned it from the orginal plumber who plumbed our house check out their work.....

    [​IMG]

    Green side drips when clothes washer is turned on..... fix it when I get around to it.....
  10. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    Let's see if I understand what is going on...
    PRV valve is not holding pressure down to acceptable levels so you adjust it down...
    Drip stops when faucet opened but starts back up when faucet closed again...
    When you adjust PRV valve to reduce pressure, faucet will run slower/less pressure but static pressure in house remains too high when nothing is running...
    .
    .
    My diagnosis is same as some others in this thread...
    PRV is failed...
    It restricts flow when throttled down but does not reduce pressure... It needs to be replaced...
    If your pressure is 140-150lb static, you will not get the T&P valve to stop dripping till you reduce the pressure by replacing the PRV.
    If you don't replace it you stand to burst a supply (clothes washer hose etc) as they are not intended for that much pressure...

    just my own $.02
  11. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA
    Check house pressure both with water running and again with everything off (static). The pressure should be no higher than 80 psi. If not, replace the PRV. Then, whatever your pressure is, (hopefully between 50 and 80,) match the expansion tank pressure to that. If it's still leaking, then you are likely exceeding the working range of that expansion tank. The manufacturer of the expansion tank that you bought will have charts for you to view to determine which size to use. If you are taking the temperature up to say 140 degrees, you may need to go up one size in exp tank.

    Also, you may want to replace the T&P again since it has gone off a few times. Make sure you use a 150psi T&P. (our policy is "if it blows, it goes")

    Is that a gas heater in a plastic pan? YIKES!
  12. Did this 2 hours ago

    First Bradford White I put my hands on in 4 years....


    Before

    after

    Pressure was spiking to 90 at night.....the water heater blew yesterday along with forcing one of my angle stops to leak.....all of a sudden from 3 years ago when I installed some Danze faucets.

    There had to be some kind of surge to cause the two to happen at the same time. Advised PRV and Expansion tank and all is well.....hot water is theirs.

    Tomorrow is a 50 gallon electric switchout. Tuesday is a gas to electric conversion.
    Last edited: Jan 12, 2007
  13. GoTanklessToday

    GoTanklessToday In the Trades

    Messages:
    89
    Location:
    Renton, WA
    Nice clean work.
  14. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    RUGGED, Up here they would require me to support the exp. tank.
    Last edited: Jan 13, 2007
  15. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    Thanks for all the feedback. Yes, PRV reduces flow, but not pressure. I'm going to change it out shortly.

    I will change out the valve on the tank, but must ask WHY? If you are supposed to flush the discharge line 1 a year you must replace them every year?

    Yeah plastic next to gas..... and the old just drain it on the floor, so why have a pan, ya know. Oh well, I might as well pull it out since it does nothing....

    Thanks again, will update when problem is fixed.
  16. Randyj

    Randyj Master Plumber

    Messages:
    1,047
    Location:
    Alabama
    Have you checked the pressue with different adjustments on the PRV? You said that you screwed out the adjusting screw... have you tried screwing it in then checking the pressure?

  17. Do they allow poly strapping up there.....or is mandated a certain gauge hanger iron?


    I always strap the larger tanks but never the smaller...but since you mention it I'll start doing that. I "prefer" to use the poly hanger strap.

    In regards to code...

    The inspectors in my area will allow a horizontal application tee'd perpendicular without strapping. <<< That doesn't make it right just because it is not required.

    It's needed because I find them all the time hanging over when the diaphragm ruptures. full of water. 2.5 gal @ 8-1/3 pounds per gallon plus the tank, 4 pounds.....roughly 25 pounds hanging on any piping system which is detrimental when those tanks rupture.

    100% of my customers don't even know they are broken until someone checks.
  18. markts30

    markts30 Commercial Plumber

    Messages:
    630
    Location:
    Phoenix, AZ
    You are supposed to flush the tank once a year...
    The hose bibb on the bottom of the water heater attaches to a gaden hose and you open it and let it run for a bit to flush out sediments to stop the tank from corroding as quickly and to stop the bottom element from burning out as fast...
    You do not use the T&P valve for this...
  19. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    Well, my water meter shutoff worked. Yeah! So while replacing the PRV I replaced the main shutoff with a ball valve. No leaks. Water heater is heating up I'm hoping the pressure stays below 150!!:eek:

    I did try adjusting the old PRV and checking pressure, both screw up and down. Pressure always creeped up to above 150, however flow at the faucets was affected.

    New one was set at 45ish, I upted it to 70, adjusted tank to 70psi, so we'll know shortly.

    I haven't replace the blow off valve yet, still the one that has gone off multiple times and been open for hours on end. We'll see what happens.:eek:
  20. harleysilo

    harleysilo New Member

    Messages:
    101
    Location:
    Georgia
    O.K. It's fixed. Tank is done heating, PSI rose about 4 from cold pressure to heated pressure!

    Thanks to all for the information and troubleshooting!

    I really appreciated it!:D
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