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Thread: Hot water out of cold taps - plumber is stumped

  1. #1

    Default Hot water out of cold taps - plumber is stumped

    Hi everyone! My husband and I bought a home about a month ago, and we immediately noticed that there was hot water coming out of the cold taps in the master bathroom. We had the plumber come out, and he is flummoxed. He simply can't find the cause. He's checked the cartridges for each of our single handle faucets and showers, but none of those is the culprit. He crawled under the house and determined that there isn't a plumbing issue - the cold water is cold under the house and the piping doesn't seem to be the issue. He is now proposing to cut holes in our walls to determine if any of the showers has a failed mixing valve which could be causing this.

    My question is: is there anything else that we should be thinking about before my walls turn into swiss cheese? Our home inspector did note a couple of things, but I'm not sure that they're relevant (my plumber doesn't think so, but other opinions would be welcome):

    * there is corrosion on the check valve for the recirculation pump for my hot water heaters (which the inspector said indicated leakage)

    * there are separate temperature/pressure valves for each water heater (I have 2 water heaters in series), but the drain pipes are connected together

    * there is no expansion tank (the report notes that certain recirculation systems require an auxiliary expansion
    tank to relieve excess pressures from the tank)

    Could any of these be the problem? What else should I be thinking about?

    Thanks!

  2. #2
    Plumber jimbo's Avatar
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    You can get a good idea about wha't wrong without tearing things up. Don't run any water for about an hour. Now go arond to all the showers, and feel the valve....best to just remove the handle and chrome trim. If one of them is crossing over, the valve will be warm to the touch. The recirc check valve is also an obvious suspect

  3. #3
    General Engineering Contractor ballvalve's Avatar
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    focus on the check valve first.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by ballvalve View Post
    focus on the check valve first.
    This would be my first thought as well...
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    Moderator & Master Plumber hj's Avatar
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    Turn off the water valves to the water heaters, THEN open a hot water faucet. IF water flows from the faucet, you have a cross connection somewhere, but do NOT let them start chopping holes in the walls until they know EXACTLY where the cause is and if a hole is even necessary. Recirculationg systems do NOT require an expansion tank.

  6. #6

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    Thanks everyone. So what I'm hearing is that my plumber isn't right that the only way to find the valve is to open up each wall near each shower. Hmm. Methinks I might need a new plumber. Anyone know of anyone in the Pasadena/Glendale area of Los Angeles?

  7. #7
    General Engineering Contractor ballvalve's Avatar
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    No holes in the walls! Take your time and live with hot water for a bit and give us some more details - you might save a fortune. If its only one room, its likely NOT the system check valve. Do you get cold water after a long run of hot water? Is it hot at toilet, sink and tub?

    When the recirc pump is on, do you have normal functions at all rooms except master bath?

  8. #8
    Moderator & Master Plumber hj's Avatar
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    Where is the circulation pump installed? At the bottom of the heater, or on the hot water discharge pipe from the heater?

  9. #9
    Licensed Plumber DrunkPlumber's Avatar
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    Easy enough to test the check valve, if it's properly installed. Simply feel the cold water supply line coming into the water heater. If it's hot you have a problem. Have seen this before where it backfeeds through the washing machine solenoid. Turn off the water to the washer and see if that solves the problem.

  10. #10

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    Thanks again everyone. To answer some questions:

    The problem is primarily in the master bathroom, although we have gotten hot water from the kitchen tap and from other bathroom taps. If there is a lot of hot water run, we will generally get cold water from the tap. For example, my husband normally showers at the gym and not at home. This morning, he showered at home, which meant we both took showers. I got nice cold water out of my tap afterwards.

    Water is hot out of the 2 master bathroom sinks and the tub. I've not touched the water in the toilet, but I do believe it's getting hot water, because when the hot water was turned off for a while, the toilet sort of sputtered like the other hot taps in the house.

    I'm not sure where the recirculating pump is - I'll have to go outside and see if I can figure that out.

    I always have the water to the washing machine off at the tap - is that what you mean?

    Thanks again!

  11. #11

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    Quote Originally Posted by hj View Post
    Where is the circulation pump installed? At the bottom of the heater, or on the hot water discharge pipe from the heater?
    OK, just went and took a look at the water heaters. The pump appears to be installe on the hot water discharge pipe (although to be honest, my knowledge of hot water heater anatomy is shaky at best).

  12. #12
    General Engineering Contractor ballvalve's Avatar
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    Maybe some pipes are run together, rather tight, and the cold is simply heating up in the pipe run. Turn off the recirc pump for a few days and see if problem goes away. This is very likely especially if you have no timer or a defective one. You do not need a plumber for that.

    If that works sell the pump, you will save a lot of money in wasted heat. Recirc pumps are just big radiators putting your hot water into the house framing.

    I'll guess that bath is pretty far from the water heater also.
    Last edited by ballvalve; 08-24-2010 at 10:18 AM.

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    IF you insulate your pipes, hot water recirculation can SAVE energy since you aren't throwing away gallons of water each time you try to get some at the tap, especially if it is on a timer so it only runs when there is anticipated use (or you save more by only allowing it to run when there is an immediate demand, but then you'll likely have to wait, but won't be wasting heated water). Even though you aren't getting hot at the beginning, you still have to heat all of that water that you dumped out as you are putting cold back into the heater. So, you might use 5-gallons to actually run the tap for a bit after it gets warm to wash your hands rather than maybe the 1/2-gallon you really used. Also, if you do not have a dedicated return line, and the recirculation is done through the cold pipe, especially if the control valve isn't working properly, the cold run from where the cross-over is will become the same temp as the hot side.

    There are various ways to install recirculation. One version uses a thermostatically controlled cross-over at the point(s) of use (no dedicated return), and the other uses a dedicated return. There is often something to either turn the pump on/off, or to throttle the flow once the end point is sufficiently warm.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Member dhla's Avatar
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    I use Estep & Sons - ask for Jerry Lenett. They are in Van Nuys, CA and phone number is (818) 782-7859.

  15. #15
    General Engineering Contractor ballvalve's Avatar
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    Jad, I have to disagree with the savings on the point of heating the water that you dumped out, as the water remaining in the feed to the tap WAS hot and it cooled off into the house air. The loss is in the water itself that went down the drain. Mom and Dad from the old country would fill their watering cans with that first run of cold water if they really needed hot at the tap. But frankly anyone that cannot wash their hands in cold [house temp] water should spend a few weeks in a campsite and learn what life was like for the past billion years.

    All these McMansions with 40 roof valleys and 4 bathrooms 400 feet apart are an abberation of society and common sense, and I fear that if things continue as they are going, they will soon learn to drink from the toilet tanks and drips from the gutters. Yes, an extreme example, but not without precedent.

    Build a home with an eye to savings of energy and careful use of space, and a centralized set of bathrooms will never need anything resembling a recirc pump. Recirc pumps are a fix for bad design work.

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