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Thread: Master Plumber and hot water heater swap out

  1. #16
    Forum Admin, Expert Plumber Terry's Avatar
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    Myth Busters video was a bit long. I have always prefered this video. And if Myth Busters had seen this video, they wouldn't have been so close to their exploding water heater.

    Augusta, that's good research on the high heat leading to the collapse of the PVC.


  2. #17
    General Engineering Contractor ballvalve's Avatar
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    That is why I am the advocate of an intermediate pressure relief valve in plumbing systems. Why would anyone rely on one valve if that is the result of its failure?

    For the OP, that water heater is a POS unless you change the joke anode rod which is about 24" long, and aluminum. It should be a 45 or 54", you can cut them with an angle grinder to just reach the bottom. Magnesium is better and now you have a 15 year water heater. Also remove the JUNK 'drain' valve and put in a full port ball valve and drain it down a bit a few times a year. When I pulled the anode on my ge 6 year job, the anode was coated with pipe dope and metallic shavings.

    http://fierychill.com/catalogsearch/result/?q=anode

    http://www.inspectapedia.com/plumbin...ter_Safety.htm
    Last edited by ballvalve; 04-01-2011 at 03:17 PM.

  3. #18
    Moderator & Master Plumber hj's Avatar
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    quote; That is why I am the advocate of an intermediate pressure relief valve in plumbing systems. Why would anyone rely on one valve if that is the result of its failure?

    PRESSURE is only part of the problem, and it makes little difference whether the pressure is 150 psi or 75 psi. When the TEMPERATURE increases due to a faulty burner control, the water is "superheated" (and accumulates a LOT of potential energy), at ANY pressure above atmospheric which is ZERO psig. WHEN the heater shell fails, or the pressure is relieved ANYWHERE, that superheated water is converted to steam with and ALL that potential energy is released with distructive force. The Mythbusters experiment was slightly flawed, but they did not redo with the revisions I suggested. Therefore, your "intermediate pressure relief valve" would NOT negate the end result of a water heater which went "wild".

  4. #19
    General Engineering Contractor ballvalve's Avatar
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    When the water is on its way to superheated, it expands and the pressure increases.

    Then the 100 psi valve opens. Even if the water in the heater is boiling, if the valve is open all you have is essentially a pot on the stove.

    Each house has other pressure relief 'valves' called fixture supply hoses, pex, and garden hoses if left on.

  5. #20
    DIY Member Hillbilly Man's Avatar
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    Quote Originally Posted by ballvalve View Post
    When the water is on its way to superheated, it expands and the pressure increases.

    Then the 100 psi valve opens. Even if the water in the heater is boiling, if the valve is open all you have is essentially a pot on the stove.

    Each house has other pressure relief 'valves' called fixture supply hoses, pex, and garden hoses if left on.
    Good thang you isn't runnin a still cuz you dunno Jack!
    Yud git yur silly azz self blowed up fer sure.
    Hillbilly Eng-in-ear
    Moonshine Maker
    Dumb as a Stump

  6. #21
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by Hillbilly Man View Post
    Good thang you isn't runnin a still cuz you dunno Jack!
    Yud git yur silly azz self blowed up fer sure.
    Well Hillbilly Man, How is it that you understand the 1:1700 expansion ratio of water to steam and our engineer friend doesn't?
    Yes his silly little relief valve is inadequate.

  7. #22
    DIY Senior Member dlarrivee's Avatar
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    Quote Originally Posted by ballvalve View Post
    Then the 100 psi valve opens. Even if the water in the heater is boiling, if the valve is open all you have is essentially a pot on the stove.
    A pot on the stove?

    Wouldn't the diameter of the pot be different than the diameter of the orifice on a valve?

  8. #23
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by dlarrivee View Post
    A pot on the stove?

    Wouldn't the diameter of the pot be different than the diameter of the orifice on a valve?
    To aid our engineer the following formula can be used...

    He is also failing to realize the set pressure of the relief valve...

    But Hey... Engineers are good at revising their work on paper when miscalculations occur.

    Even a pressure cooker only operates up to 15 psi....
    Last edited by Redwood; 04-02-2011 at 09:15 PM.

  9. #24
    Master Plumber master plumber mark's Avatar
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    Cool thank you for the pictures

    Bored again this morning
    thank you for the pictures.....

    1. the junction box is about normal that is no big deal

    2. the water lines look pretty crappy and they should have been changed out to new flex connectors.... that will come back and screw you eventually......they cost about only 10 bucks each to clean that up

    3. I guess the chimmney is no big deal, but it looks crappy just hanging there....it does keep the water heater cool with ventilation, I guess....??

    4. The PVC issue is basiacally a joke .... it will work ok for probably 100 years... but the cpvc is what you are supposed to use if it gets inspected....

    where does it release down to... just down to the floor or into the crawl space???

    5 the waterheater should have been installed in a pan with the pop off pipe dropping down into it... then the pan should have been piped into the crawl space if you have one... you can clearly see where the old heater already damaged the tile on the floor..

    as far as the water heater exploding, it aint gonna happen too often..

    that job is worse than I have seen the lowes guys and home depot do work for... I quote it at no more than $250.00.....


    actually most water heaters dont go through the roof due to the
    walls and surroundings... they usually make a good concussion
    that can damage all surrounding appliances and walls
    if it really blows, it could take out some windows
    it all depends.... but flesh and bone dont want to be
    anywhere near this event.....




  10. #25
    Master Plumber Redwood's Avatar
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    Quote Originally Posted by master plumber mark View Post
    The PVC issue is basiacally a joke .... it will work ok for probably 100 years... but the cpvc is what you are supposed to use if it gets inspected....
    Ummm Mark, It's not CPVC.... It's PVC!

    Last edited by Terry; 04-03-2011 at 10:16 AM.

  11. #26
    Master Plumber master plumber mark's Avatar
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    Cool yes it is

    Redwood, it should be cpvc and that is what I use all the time....

    but you know as well as me that the pvc sch40 will work for a hundred years.....how many potable water systems have you seen jack-legged in pvc sch40 both on hot and cold in your carreer????

    we both know it is wrong in theory....and the odds are
    their will never,,, ever be a problem with it.
    being a non pressure drain line for the heater is not
    too criticle...

    I suppose if steam literally came out of the heater
    it could eventually warp the pipe , but I doubt it would melt it......



    but just to be a pain in the ass,
    I would make him change it.

  12. #27
    DIYer, not in the trades LLigetfa's Avatar
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    Quote Originally Posted by ballvalve View Post
    When the water is on its way to superheated, it expands and the pressure increases.

    Then the 100 psi valve opens. Even if the water in the heater is boiling, if the valve is open all you have is essentially a pot on the stove.
    I don't get the "pot on the stove" analogy. Under normal circumstance, a water heater with an open TPR will be supplied with cold water at the same rate the TPR is relieving. You'd have to have one heck of a fast recovery heater to keep it boiling. Generally you wouldn't be pouring cold water into a pot on the stove as fast as it can take it cuz then it would not continue to boil and would simply overflow.
    Last edited by LLigetfa; 04-03-2011 at 11:58 AM. Reason: typo

  13. #28
    Master Plumber Redwood's Avatar
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    I guess you are right Mark...
    It will do fine until the day it is actually needed....

    Then it will just look like those pvc drain lines someone puts in a commercial kitchen for a dishwasher drain...

  14. #29
    Master Plumber master plumber mark's Avatar
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    Default will work till it fails....

    Quote Originally Posted by Redwood View Post
    I guess you are right Mark...
    It will do fine until the day it is actually needed....

    Then it will just look like those pvc drain lines someone puts in a commercial kitchen for a dishwasher drain...

    the restraunt pvc pipe is a great example of what steaming hot water does to pvc pipe...

    that is probably about right,,, the pipe might warp from intence heat or steam...but it wont actually melt away......

    I feel as long as it dont go down into the crawl space it would work fine...

    we did have one that was piped into someones crawl space that caused massive damage one time...

    the releif valve popped off and kept popping off for about a month or two...

    the people were too stupid to figure out what was going on and eventually the steam in the crawl space warped the plywood floors throughout the center of the home....

    you could write your name in the humidity on all their windows.

    the insurance company was not amused....

    ..







  15. #30
    Forum Admin, Expert Plumber Terry's Avatar
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    I don't get the "pot on the stove" analogy
    You would get it if you were a plumber.
    The water stays hot, hot enough to burn your hand. I've seen it happen when there is something wrong with a heater and the elements won't turn off.

    Things happen, and a working relief valve is only as good as the pipe draining it. Reduce the size of the relief drain, or plug it, and horrible things can happen.
    In the old days of steam power, they had engineers to prevent those disasters.
    They didn't call them engineers because they knew how to steer the trains.
    Last edited by Terry; 04-03-2011 at 12:07 PM.

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