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Thread: New gas water heater, seems to be working, but cold coming out of hot faucets

  1. #1
    DIY Junior Member chroipahtz's Avatar
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    Default New gas water heater, seems to be working, but cold coming out of hot faucets

    Hello all. I am not much of a DIYer, but I am learning due to this problem that's left me without hot water for several days now.

    My previous gas water heater sprung a leak and started leaking into the carpet, so I had it replaced. It was still providing hot water, just it was leaking and beyond repair. I have a nice shiny new unit in there now, but I am not getting any hot water to the 3 sinks and 2 bathtubs in my house; instead, cold water is coming through. I haven't tested the dishwasher and washing machine, but I see no reason to, as I'm sure they'll also be getting cold water instead of hot.

    Here are some facts: (bolded the 2 most interesting/important facts in my view)

    • After installing the new heater, there was air in the pipes, but leaving the faucets on for a few minutes returned the flow to full.
    • No leaks in the water heater or pipes coming into it or out of it that I can see. I don't think this is necessarily a hidden plumbing issue because the old heater worked.
    • Pilot light and burners are working fine. Setting the temperature higher causes the burners to come on as expected until the water is the right temperature.
    • All valves are open fully, gas valve is inline with the pipe, etc.
    • I drained some water from the tank using the drain on the tank and it is very hot, so I strongly believe the heater is doing its job.
    • The hot water outlet pipe is fairly hot (but not too hot to touch) near the tank, but it quickly gets colder and colder just a foot or so away from the tank, as it goes into the wall. Does this suggest a buildup of sediment in this pipe, so no hot water is getting out? This doesn't make sense to me either because the old heater worked.


    Going out of my mind here... I asked two of my friends who are plumbers and they don't see anything wrong with the installation and are just as stumped as I am. Remember: The old heater supplied hot water, but the new one doesn't, and it is clearly heating the water because I drained hot water from it. Any ideas? Thanks so much.

  2. #2
    Forum Admin, Expert Plumber Terry's Avatar
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    How about a picture of how the tank is connected at the top?
    800 pixels or less.

  3. #3
    DIY Junior Member chroipahtz's Avatar
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    Sorry about the quality, these are taken with an iPod Touch. Let me know if you need more detailed/closer pics.

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  4. #4
    Forum Admin, Expert Plumber Terry's Avatar
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    Well, unless the pipes in the wall are crossed, it looks like you have cold to cold and hot to hot.

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    DIY Senior Member Murphy625's Avatar
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    Make sure that red valve (on the right) on the cold water inlet is open all the way.

    Find a faucet that has separate hot and cold water valves and open JUST the hot side and let it run. This will verify that you have flow from the hot water circuit.

    If you don't have a faucet that has separate hot and cold, then you'll need to disconnect the plumbing line under the cabinet where the hot and cold lines come in and tap off there..

    If you then have flow from the hot water circuit only, and you still don't have hot water, call "Ripley's Believe It Or Not" and you'll be famous!

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    DIY Senior Member Reach4's Avatar
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    I am thinking defective water heater. Specifically I suspect the dip tube is missing or broken. This picture diagrams an electric water heater, but the dip tube would be the same for gas.

    It may be that the dip tube could be replaced in place -- I don't know.

  7. #7
    DIY Junior Member chroipahtz's Avatar
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    Quote Originally Posted by Terry View Post
    Well, unless the pipes in the wall are crossed, it looks like you have cold to cold and hot to hot.
    I thought I recalled that the previous heater was hooked up the same way. Is it possible that the old heater had its inlet and outlet switched? Again, that old heater "worked", as in, provided hot water to all the sinks/bathtubs.

    Quote Originally Posted by Murphy625 View Post
    Make sure that red valve (on the right) on the cold water inlet is open all the way.
    Find a faucet that has separate hot and cold water valves and open JUST the hot side and let it run. This will verify that you have flow from the hot water circuit.
    I think the kitchen sink has separate valves underneath, so I will try this tomorrow and let you know what happens.

    Quote Originally Posted by Reach4 View Post
    I am thinking defective water heater. Specifically I suspect the dip tube is missing or broken.
    The drain is located in the same place as it is in your diagram, and when I drained water from it, it was very hot, so that indicates to me that even the water at the bottom of the tank is very hot. I don't think the temperature of the water inside the heater is the problem.

  8. #8
    DIY Senior Member Murphy625's Avatar
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    Quote Originally Posted by Reach4 View Post
    I am thinking defective water heater. Specifically I suspect the dip tube is missing or broken. This picture diagrams an electric water heater, but the dip tube would be the same for gas.

    It may be that the dip tube could be replaced in place -- I don't know.
    I doubt it.. Could be a melted and plugged dip tube which is completely stopping water flow, but not broken.. he gets ZERO hot water.. NONE..
    A broken tube would still give him some hot water for a while.. at least good and warm.

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    DIY Senior Member Reach4's Avatar
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    Quote Originally Posted by chroipahtz View Post
    [*]The hot water outlet pipe is fairly hot (but not too hot to touch) near the tank, but it quickly gets colder and colder just a foot or so away from the tank, as it goes into the wall.
    Is this while significant water is flowing out of a hot water tap? I think this is what Murphy625 is saying.
    1. If so, this would indicate that little water is flowing through that outlet pipe. If that is the case, where is the water flowing from the hot water tap coming from? Could there be a bad temperature limiting mixing valve beyond the photos that is mixing almost 100% cold water out into the hot water pipes?

    2. If not, run a hot water tape and feel that hot water outlet pipe again. Check the temperatures at both ends again.
    Last edited by Reach4; 11-02-2013 at 10:37 PM.

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    DIY Senior Member dj2's Avatar
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    There is something in the photo that is installed in reverse, but it has nothing to do with your problem.

    The cold water supply is in the wrong order. The right order should be: shut of valve on the pipe out from the wall, then a brass nipple and the flex copper. This way you won't need to turn the water off for the entire house to work on your water heater.

  11. #11
    DIY Senior Member Murphy625's Avatar
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    By any chance did you just purchase this home?

    One other thing could be causing this issue... Someone plumbed the hot and cold lines in all the house backwards so hot in on the right and cold on the left... (reverse of normal).. Hence, you'd be opening the cold water lines.

    The reason I want you to check HOT SIDE ONLY is to make sure there is no anti-thermal siphon device that happens to be plugged closed.

    We need to verify flow before going any further.

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    DIY Junior Member chroipahtz's Avatar
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    After consulting with another friend who is a bit more experienced, we think we have the problem(s) figured out. They are two-fold:

    • The gate valve on the cold water inline has broken off, and sealed off 98% of that pipe. This happened when we initially shut it off to stop the leak (we know this because the old heater was supplying hot water to the house just fine, or at least, mostly fine). The valve is very old and had become caked with calcium, and when it was closed and then opened again, the threaded screw either became loose or broke completely. We know this because when using the emergency relief valve to remove some water, the hot water outlet pipe instantly becomes very cold. Which means...
    • There is a backflow somewhere in the house. Since the cold water inlet pipe is not functioning, the tank is pulling cold water into itself from the hot water outlet pipe. When turning on all of the hot water in the house, the hot water outlet pipe ONLY becomes hot all the way to the wall when a certain fixture is used -- the shower in the back bathroom. When turning that faucet back off, we hear in the wall that it takes a few seconds for the water pressure to stop, meaning the water is backflowing somewhere.


    Now, I don't claim to be a plumbing expert, nor does the friend I had over, but this makes sense to me. Our current course of action is to have a plumber replace the gate valve, or bypass it (we were unable to remove it). I am posting this here for a second opinion from people who know their stuff. Can you please tell me if what I've described sounds correct, or even if it was completely nonsensical? I can try to reword it if so.

    Here is a more detailed picture of the piping on top of the water heater. The blue valve at the top is the gate valve that we discovered is broken.

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    Last edited by chroipahtz; 11-04-2013 at 10:57 AM.

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    Forum Admin, Expert Plumber Terry's Avatar
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    A 98% closed off shutoff to the water heater?

    1) That should be removed and replaced with a new shutoff.
    Pick up a new flex while you are at it. We never reuse old flex.

    2) Get rid of the shutoff at the top of the water heater.

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    When a gate valve fails, often it's the stem breaks off from the actual gate, and the handle will just spin. I can't see how the valve at the wall is connected, but if it is threaded, you could just install a new one. I'd prefer to use a ball valve verses a gate valve.

    If you shut off the supply to the WH, and you can get water out of both the hot and cold taps around the house, you have at least one valve that needs to be fixed as it is creating that cross-over. One way to do that is to start to shut the hot supply at the wall off to those valves, one at a time (your shower may not have any) until that flow stops, then you know you've found the one that has the cross-over. You don't need to worry about any two-handle faucets, only those with a single handle.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member chroipahtz's Avatar
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    Quote Originally Posted by jadnashua View Post
    When a gate valve fails, often it's the stem breaks off from the actual gate, and the handle will just spin. I can't see how the valve at the wall is connected, but if it is threaded, you could just install a new one. I'd prefer to use a ball valve verses a gate valve.

    If you shut off the supply to the WH, and you can get water out of both the hot and cold taps around the house, you have at least one valve that needs to be fixed as it is creating that cross-over. One way to do that is to start to shut the hot supply at the wall off to those valves, one at a time (your shower may not have any) until that flow stops, then you know you've found the one that has the cross-over. You don't need to worry about any two-handle faucets, only those with a single handle.
    Thanks, this is basically exactly what he told me (to use a ball valve and to find the cross-over). All of them have two handles, and the only shutoff valve I've seen for any of them is on the kitchen sink.

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