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  1. #1
    Join Date
    Dec 2019
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    Showers cold - sink faucets hot

    Hi everyone,
    Just bought a new house and working out the kinks. As of recently both showers/tubs have hot water only for a minute and then cool down. Iíve tried running the sink faucets at the same time and they fluctuate similar like the shower but then recover and stay hot. The domestic hot water is coil fed from the hot water boiler. The temp settings on the boiler are 190 high and 170 low, so there is plenty of hot water at the boiler. For whatever reason, it canít get to the showers. I pulled off the shower handles and there doesnít appear to be an anti scalding device. It sounds to me like the coil is going bad, but then I donít get why the faucets are staying hot. Any ideas? I was thinking of setting up a separate hot water tank but I want to make sure thatís the problem here. Thanks!

  2. #2
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    Dec 2019
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    Thread Starter
    Update: my wife showered when the boiler was sitting at 170 and the water was luke warm. I showered a half hour later after the boiler had recently called and was at 190 and the shower was hot. For whatever reason, it appears the boiler needs to be very hot to have consistently hot water.

  3. #3
    Join Date
    Oct 2011
    Location
    Gladstone, Oregon (Portland)
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    Quote Originally Posted by Joe85 View Post
    Update: my wife showered when the boiler was sitting at 170 and the water was luke warm. I showered a half hour later after the boiler had recently called and was at 190 and the shower was hot. For whatever reason, it appears the boiler needs to be very hot to have consistently hot water.
    Not going to get into it too much but that my friend, is a shower mixing valve issue. Call a plumber!!

  4. #4
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    Dec 2019
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    Thread Starter
    Quote Originally Posted by Adlerberts-Protege View Post
    Not going to get into it too much but that my friend, is a shower mixing valve issue. Call a plumber!!
    Thanks for the response, thats what I originally had thought but the same issue is happening in different showers/bathrooms e.g. when the boiler was at 170 both showers were cold, at 190 both showers are hot.

  5. #5
    Join Date
    Oct 2011
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    Gladstone, Oregon (Portland)
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    Quote Originally Posted by Joe85 View Post
    Thanks for the response, thats what I originally had thought but the same issue is happening in different showers/bathrooms e.g. when the boiler was at 170 both showers were cold, at 190 both showers are hot.
    Somewhere cold and hot are mixing. That is a certainty. A plumber will figure it out quickly.

  6. #6
    Join Date
    Jan 2012
    Location
    Broomall, PA
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    Do you have a mixing valve at the coil at the boiler?
    First step would be to measure temperature coming out of the boiler, and temperature after the mixing valve. Mixing valves fail to the cold. Also as it gets colder outside, the cold water gets obviously colder and you get less output from the coil.
    Most tankless coils are only rated between 3 & 4 gpm flow rate when new.
    What’s the gpm flow rate on the shower head?
    170-190 is too high.
    If the testing shows the temperatures are not correct and you are not exceeding the flow rate, the next step is to get a boiler tech to clean/flush the coil (boil the coil). This can be done with or without chemicals, but must only be done by someone who has the proper skill and knowledge to do it. It’s not a 'look it up on YouTube' deal as many of those are just plain wrong or dangerous. Properly done will clean both the boiler side and the water side.
    If that fails to restore adequate hot water production, thn you have 3 options:
    1. Replace the coil. Least expensive option, but when done you still have 100 year old technology, the worse and more expensive way to produce domestic hot water. Also, could turn into a real hard and potentially expensive job if you can’t get the bolts off, or they break.
    2.Abandon or blank off coil, and install a separate stand alone water heater.
    3. Abandon or blank off coil, and install a small indirect.

    Properly sized and installed, the indirect is the most expensive for install, but most economical in operating costs, and usually endless hot water.
    A little less expensive than the indirect is the standalone water heater, but costs more to operate.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

  7. #7
    Join Date
    Jan 2004
    Location
    PA
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    You may have another faucet somewhere bleeding cold water into the hot water pipes.

    Also could be that your over tapping the tankless coil. Post model number and brand of boiler, so we can check what size tankless coil it has.
    Contractor locator map

    How-to-apply-for-Professional

    How many times must one fix something before it is fixed?

  8. #8
    Join Date
    Dec 2019
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    Thread Starter
    Thanks for the replies everyone. I do have a mixing valve at the boiler and I suspect itís the culprit. Iíve been thinking of getting the domestic hot water off the boiler and putting in a separate electric hot water tank, this is probably a good time to do it. I gotta imagine a new mixing valve and separate hot water tank will resolve the issue. Thanks everyone.

  9. #9
    Join Date
    Jan 2012
    Location
    Broomall, PA
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    You could buy a new, same mixing valve, isolate and drain, replace the guts of the old valve with the guts of the new to see if that fixes it.
    I would get a small indirect and pipe it as it’s own zone over a stand alone electric water heater, even if your electric rates are low.
    If I do a job in 30 minutes it's because I spent 30 years learning how to do that in 30 minutes. You owe me for the years, not the minutes.

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