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Water heater adjustments

nater | Posted in Energy, Heating & Insulation on February 8, 2006 05:04am

I’ve got a problem with my water heater – I’m not sure what brand it is, but is a NG 40 gallon that was in the house when I got it.

It heats up fine to get hot water, but not always. It seems like the cycles are too long and the water cools down too much. Depending on when I catch it, I can get either semi-scalding water, or lukewarm water. Is there any adjustment I can make to change the minimum temperature? I don’t really want to raise the temperature and risk having kids get burned.

Thanks in advance!

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Replies

  1. User avater
    rjw | Feb 08, 2006 05:33pm | #1

    That is a common problem with water heaters: there is only the one temp sensor: as the burner fires up, the hottest water rises and forms a "layer" at the top and can get very hot before the burner turns off.

    See my article on scalding risks at http://pi-inspect.com/ParaFiles/ParadigmScaldHazards.pdf


    View Image
    Sojourners: Christians for Justice and Peace
  2. DanH | Feb 08, 2006 05:55pm | #2

    It could be a problem with the distance between on and off setpoints in the thermostat, but don't know that there's any way to adjust it.

    This can also be caused by a buildup of sludge in the heater.

    But the first thing to check is the dip tube. There was a batch of bad dip tubes made some years back, and the last few of them are probably failing right now. The dip tube deposits the cold water in the bottom of the tank, and if it breaks off you can get cold water mixing with the hot at the top of the tank.

    If ignorance is bliss why aren't more people

    happy?

    1. User avater
      nater | Feb 08, 2006 07:27pm | #3

      I'd have to agree with you, I have flushed the heater several times, and it isn't that old (replaced just before we bought the house from the seller 2years ago) unfortunately we don't have any documentation on it.

      1. DanH | Feb 08, 2006 10:10pm | #6

        Check the manufacturing date on the nameplate. I don't recall how old a unit must be to have a bad dip tube, but I suspect that some units 4 years old or so may have them.
        If ignorance is bliss why aren't more people

        happy?

    2. BryanSayer | Feb 08, 2006 08:23pm | #4

      I had one of those bad dip tubes. Got it replaced on January 2nd. Of course, the refund ended December 31st!Anyway, if you have one of the bad plastic dip tubes, you will probably find tiny pieces of plastic in the faucet screens.

    3. User avater
      rjw | Feb 09, 2006 02:49pm | #7

      How woukld a bad dip tube lead to very high temps being drawn off the top of the water heater?So far as I know, the dip tube problem only results in shortened availability of hot water, not in layering.

      View Image

      Sojourners: Christians for Justice and Peace

      1. DanH | Feb 09, 2006 06:54pm | #8

        Simple. Wife complains that water is cold, so hubby turns up the thermostat.Depending on the phase of the moon -- ie, what currents are flowing inside the heater -- one may get a fairly good supply of hot water at one point and virtually all cold water at a different point.

        If ignorance is bliss why aren't more people

        happy?

        1. finehomerebuilder | Feb 21, 2006 04:57am | #9

          OK, how does one check for a bad dip tube?And how does one replace a dip tube?(These questions as to a fairly new Sears gas water heater that has the same symptoms described by the original poster of a very wide water temperature range, particularly if hot water hasn't been drawn from it for several days, when it then starts out at lukewarm and only heats up properly after quite a bit has been drawn off.)

          Edited 2/20/2006 8:59 pm ET by finehomerebuilder

          1. DanH | Feb 21, 2006 05:27am | #10

            If it starts out lukewarm then it's probably not the dip tube. The dip tube problem would cause the water to go cold farily rapidly after only a relatively small amount of "normally hot" water was withdrawn.There is the problem that can occur, especially in a replacement situation, where the inlet and outlet are reversed, due to an oddity in the configuration of the pipes. Basically the dip tube is in the wrong hole and so cold water is drawn from the bottom of the tank. After drawing some water the incoming water will mix things up a bit and the water coming out will become warmer.Figure out which pipe is the "in" and which is the "out" on the unit (based on your study of where the pipes go), then look closely at the top of the unit for "in" and "out" embossed near the pipes. If the embossed words don't match reality then likely the unit is installed backwards, and the dip tube needs to be removed from the hole embossed "in" and installed in the hole embossed "out".

            If ignorance is bliss why aren't more people

            happy?

  3. whoover | Feb 08, 2006 09:25pm | #5

    It is true that some temperature swing is expected due to the dead band in the Thermostat...the difference in the temperature where the thermostat turns on the burner and when it turns it off.  That dead band should be somewhere around 15 degrees.  It sounds like the swings you are experiencing are much more than that.  If so, call the company that made the heater since it is still under warrantee. 

     

    If you know the brand and model number, you will be able to get manuals, etc. on the internet.

     

    Bill

  4. MrBill | Feb 21, 2006 06:51am | #11

    nater,

     If you figure it out, let me know ! I have the same exact problem with an AO Smith gas water heater we installed about 4 years ago. AO Smith says it is normal, apparently there is a big difference between the "on" and "off" temp of the gas valve. First thing in the AM I get luke warm water. After one shower, it will get up to normal temp and stay there as long as you want, if you are using water. But ... let it sit for more than a few hours and you are back to lukewarm again. I personally don't buy thier reasoning, I remember always being the first one up when I was a kid and we always had good hot water first thing in the AM. That was with a gas heater also, probably terribly inefficient, but it made hot water ! Probably something having to do with modern people not having the sense to check the water temp before stepping into the shower and scalding themselves. Personally, I like it steaming hot and dont think it should be a problem.

      By the way, this water heater replaced an electric one that never had a problem steaming up the shower first thing in the morning.

    Bill Koustenis

    Advanced Automotive Machine

    Waldorf Md

    1. rich1 | Feb 21, 2006 09:06am | #12

      It's a real condition and most w/h companies have service bulletins describing it.

  5. arrowshooter | Feb 21, 2006 11:28am | #13

    The problem you describe can also be caused by a defective TP relief valve.

    The spring in an old pop off valve can get weak and cause it to open from time to time when it should'nt.

    Run the discharge line from the TP valve into a 5 gal. bucket outside and check to see if it is discharging water.

     

     

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