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Thread: Water in bottom of tank - and - hot water in cold lines

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  1. #1
    DIY Junior Member SteveRiley's Avatar
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    Default Water in bottom of tank - and - hot water in cold lines

    I am unsure of whether my symptoms reveal two problems or if they're related. Anyway...

    Friday morning, my wife complained of no hot water for the shower. When I went to investigate the water heater, I noticed a small puddle surrounding it, a circle approximately two inches wider than the base of the heater. I peeked into the pilot light viewport and saw that the light was out. I re-ignited it, waited a minute, then switched on the burner. The burner lit, and then extinguished, along with the pilot light.

    Thinking I had a leak of some kind, I called the company that installed the system in January 2008. The plumber removed the door at the base of the heater and noticed standing water. He vaccuumed out about one third of a gallon, he estimated. He waited a bit and noticed no leaks. He lit the burner and let it run for a while. Again, no leaks. We discussed the situation, and he concluded that the problem is condensation, because the heater is sitting directly on a concrete floor and can't get enough air for combustion. He said to keep an eye on it, and if the problem returns, they'll come install a stand to raise the heater to improve airflow. This would not be covered by the heater's warranty, of course, and I'd have to "pay a little bit."

    On Saturday I noticed some water around the heater again. And on Sunday, my wife's shower ran out of hot water. I opened the door on the heater and -- sure enough -- the problem had returned.

    I have spent a few hours reading through various posts on this forum and others and have concluded that the condensation diagnosis is wrong. The volume of water just seems too great, and why would I just now have a condensation problem?

    Possibly related (or not), for a few weeks now, I've noticed that very hot water will come out of our faucets when the cold side is opened. This happens if no water water has been flowing through the house plumbing system for a few hours. I mention this second symptom because I don't know if the two are related.


    Here is a diagram of my hot water system:




    The expansion tank, installed at the same as the water heater:




    The check valve; this is the original valve that came with the house, built in early 2002:




    And the tank itself. Note that the T&P valve is piped outside:




    When I looked outside, there was no water where the pipe exits the house.


    Now for my questions.

    Why is hot water entering the cold water pipes? Isn't the check valve supposed to prevent that backflow? I'm wondering whether the valve is damaged. The valve is now 10 years old. When I tap the side of the expansion tank, it rings hollow for the upper 75% of its height. Water does not spurt out of the Schrader valve. The pressure at the valve is 65 psi. I have not depressurized the system to check the tank's pressure in that state. I suspect the tank is OK.

    Where could the water in the bottom of the tank be coming from? Do T&P valves leak inside the space between the heater's jacket and internal tank?

    I am somewhat reluctant to call this plumbing company again until I have a better understanding of possible causes. Thank you for reading this post, I know it's long, but I wanted to ensure I covered all the details.

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    Chances are pretty good that your tank has a pinhole rusted through it. The water runs down tank under the insulation and drips onto the burner, extinguishing the pilot. This would not explain why your hot water is crossing over, which is sometimes caused by a bad shower mixing valve or someone using a shut-off on a shower head.

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    Forum Admin, Expert Plumber Terry's Avatar
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    That's an interesting concept having a check valve between the expansion tank and the water heater. It kind of prevents the expansion tank from working.

    It sounds like you have a leak. If you need plumbing, give me a call. I normally charge about 1/2 of what your plumber is charging.
    Of course he offers coupons. But I will honor several of his coupons, if I can take them off "his" pricing. That's still a lot more then I'm used to getting.

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    DIY Junior Member SteveRiley's Avatar
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    Hi, Terry. I figured you'd recognize the installer. When the original water heater fell apart in 2008 (after six years of service), it was on the Sunday morning before I was scheduled to depart for a three-week international trip. Understandably, my family wanted it fixed now, and the installer I chose was the only one available right then. Sigh.

    I've posted my question on another forum, and someone there picked up on the same detail you did. I am now quite curious why the house's original plumber decided to put the valve there?

    The tank is still under warranty, so I suspect I need to continue to deal with the installer.

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    Forum Admin, Expert Plumber Terry's Avatar
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    Putting the check valve there puts a lot of stress on the weld joints. The expansion tank was supposed to prevent that. However, placing the check valve there may have led to the premature death of the water heater tank.

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    DIY Junior Member SteveRiley's Avatar
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    OK. I know I shouldn't have done this, especially since I myself am a forum admin, but I simplified my earlier diagram to try to keep the post from getting too long or complicated. Because this curious check valve has aroused suspicion, it seems important to provide more detail.

    Here's a complete diagram:



    The water heater heats the house by sending hot water to six fan coil radiators. Cold water enters the system and hits a tee (1). One output goes to a mixing valve, the other output passes through the curious check valve and into the water heater. Hot water exits the heater and hits a tee (2). One output goes to the mixing valve, the other output goes to the fan coils (via an electric circulator). Water from the fan coils re-enters the water heater via a tee (3) in the cold line after the curious check valve. Since this system requires a higher water temperature, the mixing valve combines some cold water with the hot water to reduce the temperature of the water that goes to faucets.

    The question mark points to the curious check valve. I can see why this valve would impede expanding water from getting to the tank. Perhaps this valve is installed to ensure that water from the fan coils flows only into the water heater and not back into the cold water supply? (Remember, this is the original design as configured by the builder of my house in 2002, not something done during the tank replacement in 2008.)

    Also: I close the ball valves near tees 1 and 3 until winter sets in because water rises through the piping into the fan coils even when the circulator isn't running. The house has many south and east facing windows and it simply gets too hot if I don't shut off the water. Recall the second problem: hot water coming out of faucets in the cold position -- this implies that hot water is somehow getting past the curious check valve anyway. As an experiment, I opened the ball valves today and plugged in the circulator. Hot water flowed through the fan coils as usual. Interestingly, hot water no longer appears when the faucets are opened to cold! It's as if the additional piping for the fan coils provides sufficient expansion space now.

    Lots of words, I'm sorry. To sum: given what you see now, would you still recommend removing the curious check valve?

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