Water Heater leaking from T&P valve

Discussion in 'Water Heater Forum, Tanks' started by misterfixer, Jan 28, 2010.

  1. misterfixer

    misterfixer New Member

    Messages:
    5
    Location:
    Charlotte
    New member here with a small problem at work. This is an electric, 50 gallon WH. New resident moved into a unit, there are 3 adults bathing, washing clothes and dishes. Resident says water is showing up in drain pan of WH. Felt inside of pipe from T&P valve-it was wet inside. Replaced T&P, next day water in pan again. Thermostats are set @ 120F, and checked at faucets - 118F to 125F. Third call out, and the boss says we will replace WH. Guess what??? Water in pan again today. Never have seen this happen with previous residents, or in any of the other 275 units on the property. I understand about thermal expansion, but I cannot figure out how this problem cropped up with the only variable being more residents in this unit. Checked water pressure in this unit, and it read 68psi. Anyone have any ideas, or should I mention installing an expansion tank to my boss?
  2. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,236
    Location:
    Land of Cheese
    Monitor the pressure gauge over several hours, the pressure can change greatly over the course of a day in some areas. Your building might need a new PRV and the expansion tank also.

    Most areas require a licensed plumber to work on multi-family structure plumbing.
  3. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    Sounds exactly like what one would get from thermal expansion: more residents (and winter incoming water temps) = more thermal expansion and higher pressure spike. Have you not placed a test gauge on the waterlines overnight? That would have been the first thing to check if the T&P was not actively leaking when you arrived. If you see the pressure spike overnight it will confirm if the T&P is doing exactly what it is supposed to do. Rather than waiting overnight you could fill a tub with hot water until the temperature started to fall off, then allow the water heater to reheat while the gauge was connected. After an hour or two you will have your answer.

    In my own case I discovered that I needed a thermal expansion tank through the above methods after replacing the toilets. The old toilets' fill valves seem to have been leaking down when pressure hit 100-120 psig because that is what I had read on the test gauge several times before that and there were not T&P drips then. After the toilets were changed I noticed some water drips after morning showers. I put the test gauge back on and it confirmed spikes to 150 psig.

    Also, have you considered that prior tenants might never have noticed or cared enough to mention a small amount of water in the pan? I'm amazed at the problems that people will ignore or fail to note.
  4. Redwood

    Redwood Master Plumber

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    Location:
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    You won't even have to wait an hour or two to see the pressure increase from thermal expansion.
    Just deplete the hot water and watch the gauge climb.
  5. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    With it being an electric and their much slower recovery time, I hedged. The max temp and therefore max thermal expansion won't be reached until the tank has recovered...although the T&P might begin relieving much sooner than that. There might be some other parts of the system taking up some of the thermal expansion.
  6. Redwood

    Redwood Master Plumber

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    7,453
    Location:
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    Here's where the difference from an engineer and an plumber come in...
    One relies on data and the other has watched the pressure gauge climb rapidly many times...
  7. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    Observations are part of the data. And what I observed with my own T&P was that the pressure rose the whole time the burner was running until the relief pressure was hit. It was near the end of the burner's run when it would relieve if at all. Our usage rate is not high so I'm not surprised by this. But I have to anticipate that others' systems might have higher usage rates and perhaps a slowly dripping faucet or such that would alter the scenario. (It's an example of providing more robust advice rather than simply jumping to a conclusion.) So if one wanted to see this in an electric heater and cover all the bases to determine if the T&P is popping due to thermal expansion the duration would be considerably longer.

    Understanding why and what extremes to look for is the difference between an engineer and a plumber.

    A water heater is a pretty simple case compared to all the scenarios one has to consider for thermal expansion joints/bellows on the shells of 600 and 1200 psig steam process heaters (with superheat cases to boot.) Start up, shut down, failed/stuck control valves or instrumentation, loss of utility side, pump failures, etc. all have to be considered to determine the design case. One has to consider not only unexpected failures, but operator error.
  8. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    It is not necessary to wait till the T&P discharges to understand what is going on unless you want to waste time....
  9. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    How many units in this building...I would check for a check valve or PRV in this unit, separate from the building...does the building have a PRV or check valve...check the WP over time with a lazy hand pressure gage...leave it on for 24 hrs.
  10. Redwood

    Redwood Master Plumber

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    Location:
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    Of course if i was the type of plumber Bison imagines me to be I'd be sitting there with a clipboard and a stop watch taking pressure readings by the minute to make a pretty graph to present to the customer...

    Personanlly I'd just go and look at the base pressure before running anything to make sure its stable and there isn't a bad PRV.
    Then I'd deplete the tank and close it up watch the pressure climbing hit a faucet real quick to watch it drop once or, twice then.
    I'd go get the parts I need and get on with it...
    No sense in wasting time and the customers money....

    Its a pretty simple system with a simple diagnosis.
    No sense in making it more complicated than it really is...
  11. Runs with bison

    Runs with bison New Member

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    891
    Location:
    Midwest
    Redwood should change his user name to Redstraw since all he does is put up worthless strawman arguments. Keep trying Redstraw, you'll eventually score a point. <yawn>
  12. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    Your replies are so...

    [​IMG]

    I suggest reading my signature...
    Then applying it...
  13. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    I suggest you read your signature, understand it, then apply it. Of course you always fail at step #2.

    Besides, we already know what you would have really done in this situation. You would have told them they needed to install a new BW water heater...you aren't exactly the sharpest pencil in the box.
  14. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,804
    Location:
    New England
    Let's make this fairly simple...if the pressure rises without the WH running, there's a PRV problem. If it rises while the WH is recovering, it is an expansion tank problem. You only need to know which situation is occuring and note the trend...the solution is obvious, and easy to fix. Now, an engineer might find it interesting to compare the pressure rise with the volume of the tank and verify the correct size of the expansion tank and see if it correlates with his calculations...a plumber knows what's required to make the customer happy and just does it saving the customer time and therefore money. Once the engineering is done, the customer doesn't need to pay for the experiment whose outcome can be quickly and easily recognized based on his experience.

    Let's keep this from throwing barbs...there's a difference in providing a service at a reasonable cost and and engineering exercise to discover new things. this isn't rocket science, been there, done that.
  15. Runs with bison

    Runs with bison New Member

    Messages:
    891
    Location:
    Midwest
    Jim,

    My original point, which has been distorted by Deadwood's errant crusade, was to determine if it was thermal expansion. I gave several ways of doing so: passive as in waiting overnight and active as in doing the test oneself by discharging hotwater and monitoring pressure during recovery. Only a simpleton like Deadwood/Redstraw would have to stay by the gauge the whole time. (Even you fell for his strawman claim about what I was saying, nothing is more irritating that having a buffoon like that shape one's image. Just another reason to loath a disengenous scumbag like him.) Afterall, that's what the red needle is for on the test gauge and is how I've used it. Furthermore I went into several "why's" of how this could be happening now but was not observed before. (I could have/should have added that other unrecognized changes such as fixing a dripping faucet or replacing a toilet/fill valve could also reveal the sort of symptoms observed.) This was to answer the OP's question in an inclusive enough way to help him find the solution. I made the assumption that the OP needed a bit more thorough analysis and reasoning based on their initial post.

    A key consideration is how high the pressure is getting. If it's not getting anywhere near 150 then the T&P should not be opening. If it is getting that high then it is either a supply issue, or thermal expansion. Unless the main pressure is close to 150 even a failed PRV wouldn't be the primary culprit although it could very well be a contributor. As it is, the OP probably knows the approximate main pressure for the 275 units already. It is hilly here and in some low lying areas near the water towers/pumps the pressure is close enough to 150 psig that plumbers have commented to me about T&P relief/PRV problems in those areas.

    But what do I know? I'm just an engineer who quickly figured out that the BW pimps' longtime theories on the Flamelock problem weren't accurate much of the time...and also figured out that the shared Unitrol Robert Shaw valve was the culprit in a large quantity of the problems...something that could save a homeowner around $800 compared to following Deadwood's standard "advice." Going counter to some clique's theories is nothing new to me, I've been through these sorts of root cause battles with other engineers and corporate execs before and have the battle scars to show for it. The underlying system doesn't care how we think it works, what matters is whether we interpret the data correctly to understand it and then profit from understanding it. I've had R&D Directors tell me I didn't know what I was talking about with a system that had been running 20 years, then a year later recall that mistake when toasting the success of my solution to a long standing problem, admitting,"You know, I thought you were nuts when you said it worked like this..." I let the data, observations, calculations, and established engineering principles guide me to the root cause and solution, not the opinions of a PhD chemist, MS engineer, master plumber, operator, or mechanic.

    Heck if you want a real laugh, ask Deadwood to regurgitate and interpret the legal boilerplate in BW's comments on water heater jackets. He couldn't reason his way out of paper bag.

    So what really matters is whether or not the OP gets enough of an explanation to determine what is happening and why, not what Deadwood thinks or what I think.
  16. Redwood

    Redwood Master Plumber

    Messages:
    7,453
    Location:
    Connecticut
    Give it a rest Laddy!

    No where in this thread was it discussed about replacing the water heater with a Bradford White, Whirlpool water heater problems, Robert Shaw gas valves or, any of the like. Your inability to separate issues from one thread to another is muddying up the messages of many threads and is off topic in many cases.

    The testing to determine whether a thermal expansion tank is needed is a simple and quick test that we plumbers have outlined above and really doesn't require overnight pressure testing or, monitoring to see the pressure increase to 150-psi with watching for a T&P discharge. we simply see the pressure climbing from the thermal expansion and go ahead with installing a thermal expansion tank. It's that simple!

    The primary difference between a plumber and an engineer is we plumbers bring a broad base of knowledge to our customers and look out for their interests. You as an engineer bring highly specialized knowledge in a specific area of expertise to the table. In some cases this is similar to a horse wearing blinders which limits its broad view.

    I'm going to bring in an area of engineering that your narrow focus has ignored in this debate. Your insistence on the pressure being allowed to go to 150-psi before saying the thermal expansion is "the" problem actually allows another factor to come into play. The tank of the water heater is a pressure vessel and part of its design is an expansion and contraction that occurs with changes in pressure. Each cycle of pressurization has an effect on that pressure vessel in the form of metal fatigue and in the case of a glass lined tank on its liner. Eventually these pressurization cycles will cause enough cracking of the glass lining and fatigue cracking of the metal that a premature failure of the tank will occur. This process happens with many different types of pressure vessels every day and was demonstrated in a dramatic fashion a few years back on Aloha Airlines Flight 243.

    [​IMG]

    [​IMG]

    I respect your knowledge as an engineer with your discussions on thermo dynamics but at some point the discussion shows the limitations of your being a specialist which by definition is someone who knows more and more about less and less. Really try sticking to what you know best, it will make you appear to be much more intelligent than trying to bounce everything I say back at me or, carrying your narrow discussion across every thread on the board. Solutions to many problems are quite a bit simpler than you imagine. In this case the installation of a thermal expansion tank is justified and will minimize the pressure cycling keeping the pressure stable at the supplied pressure within a couple of pounds. If the supplied pressure is above 80-psi a PRV should be installed on the system, this is where 24-hour pressure monitoring would apply.
    Last edited: Feb 1, 2010
  17. Cookie

    Cookie .

    Messages:
    5,660
    Location:
    .
    You actually call people "scumbags" and for what reason?



  18. redwoodvotesoften1

    redwoodvotesoften1 New Member

    Messages:
    78
    That be some strong talkin Bison.
    To me i'm a wundrin whether your a

    [​IMG]

    or, a

    [​IMG]

    cause you sure like ta

    [​IMG]

    Jess my $0.02
  19. misterfixer

    misterfixer New Member

    Messages:
    5
    Location:
    Charlotte
    Sorry for taking so long to return. We had significant weather in NC this past weekend. We will be installing an expansion tank in this apartment tomorrow. A bit of engineering will be necessary because of the CPVC piping. The boss wants to be sure we have the tank well supported. Pressure readings seem to stay in the 60 psi range, so that is what we will preload the tank to before installation. Thanks for your replies.
  20. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    let us know if that works...The problem is if the PRV and /or check valve is on the building main every unit will require a tank or you can place 1 big one where the PRV is...
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