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  1. #1
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    Dec 2007
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    Default Not enough hot water to fill the tub

    I'm trying to figure out what might be wrong with my water heater. We had a new 40 gallon tank installed in August 2006. For the last 6 months or so, we've noticed that when we run the water for a bath to bathe our kids, we have to turn off the cold water before the tub is filled because the water coming from the faucet has cooled off. It starts out hot, then after about 5 minutes it cools off, so eventually just the hot is on but lukewarm water is coming out. This is the case whether we've done laundry all day or we've been out of the house all day using no hot water. We had the utility company (who installed it) come out once & they assured us the tank is working fine. It's a gas fired water tank. We certainly aren't getting 40 gallons of hot water; we're not even getting enough to fill a tub. We have the temp setting on "A", about 120 degrees. What's going on here?

  2. #2
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    Jun 2007
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    Default Re: Not enough hot water to fill the tub

    Quote Originally Posted by dave_mc View Post
    I'm trying to figure out what might be wrong with my water heater. We had a new 40 gallon tank installed in August 2006. For the last 6 months or so, we've noticed that when we run the water for a bath to bathe our kids, we have to turn off the cold water before the tub is filled because the water coming from the faucet has cooled off. It starts out hot, then after about 5 minutes it cools off, so eventually just the hot is on but lukewarm water is coming out. This is the case whether we've done laundry all day or we've been out of the house all day using no hot water. We had the utility company (who installed it) come out once & they assured us the tank is working fine. It's a gas fired water tank. We certainly aren't getting 40 gallons of hot water; we're not even getting enough to fill a tub. We have the temp setting on "A", about 120 degrees. What's going on here?
    Three possibilities come to mind. 1] a broken or missing dip tube so the cold water is mixing with the hot instead of being feed into the bottom of the tank 2] the water heater hook up is back-wards with the cold water going into the hot outlet and the hot coming from the cold inlet side 3] with that low a temp setting if the lower element in the tank is bad you may not be heating the whole tank.
    Hope that helps,
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  3. #3
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    Dec 2007
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    Default Re: Not enough hot water to fill the tub

    Thanks- I suspected the dip tube but since the tank was less than a year old when we began experiencing this problem, I thought it was an unlikely cause. We have a low flow shower head in the master bathroom so we don't experience the cooling off problem; our tub is standard size and we only need enough water in it to bathe two young kids, so it's not like we're trying to fill a hot tub.

    I doubt the problem is distance from the tank to the tub, as the tub is about 20' directly above the tank. Insulating the pipes would be tricky; they run inside the insulated exterior wall for the entire run.

    The most vexing problem is that until our original water heater failed (after 20 years), we never had the problem we're having now. It's only with this brand new tank that we've been running low on hot water. The old tank was the same size as this one.

    I'll have the utility come out to drain and check the dip tube.

  4. #4
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    Dec 2007
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    Default Re: Not enough hot water to fill the tub

    Quote Originally Posted by JLMCDANIEL View Post
    Three possibilities come to mind. 1] a broken or missing dip tube so the cold water is mixing with the hot instead of being feed into the bottom of the tank 2] the water heater hook up is back-wards with the cold water going into the hot outlet and the hot coming from the cold inlet side 3] with that low a temp setting if the lower element in the tank is bad you may not be heating the whole tank.
    Hope that helps,
    Jack
    Jack- thanks; I think #1 might be the answer. #2 isn't it; it's hooked up correctly. #3 isn't it; it's a gas-fired tank so there isn't a lower element. The only thing that worries me is that if it was a dip tube problem, I'd think I wouldn't even get as much hot water as I do- if the cold is mixing with the hot at the top of the tank, I'd expect all water to come out lukewarm or cold, rather than having several minutes of hot. But I'll check it out. Thanks.

  5. #5
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    Default Re: Not enough hot water to fill the tub

    Dave,
    Sorry I missed you saying it was a gas unit.
    The tube may not be completely missing, it could be boken off and short.. plus most of the cold water will drop to the bottom of the tank it is not a complete mix in the top.
    Jack
    Be sure you live your life, because you are a long time dead.-Scottish Proverb

  6. #6
    Join Date
    Aug 2007
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    Georgia
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    Default Re: Not enough hot water to fill the tub

    I really think you need to turn up the temp. It sounds like your simply running out of hot water. With a higher setting at the heater you are mixing less hot with teh cold water at the tap. So if you raise the temp you will actually use less hot water. Give it a try. What have you got to lose?

  7. #7
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    Aug 2007
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    Default Re: Not enough hot water to fill the tub

    Dave ... i agree with the mention of the dip tube likely being the problem.
    It may be there is a crack in the tube part way down in the tank

    As you mentioned it's only about a year or so old but it can still happen ... besides there should be some kind of warranty for that.

  8. #8
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    Dec 2007
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    8

    Default Re: Not enough hot water to fill the tub

    Quote Originally Posted by tbgworldwide View Post
    I really think you need to turn up the temp. It sounds like your simply running out of hot water. With a higher setting at the heater you are mixing less hot with teh cold water at the tap. So if you raise the temp you will actually use less hot water. Give it a try. What have you got to lose?
    Actually, what I have to lose is quite valuable. I have two young daughters and they're used to adjusting the taps to a comfortable temp for washing their hands; I'm afraid I'd risk burning them if I increase the temp too much. I'd have to put an anti-scald mechanism in before doing that. Plus, with a gas-fired tank where the water heats from the bottom, I can't imagine a 40-gal tank running out of 120 degree water in 5 minutes, making me turn off the cold completely. There should still be 40 gallons of 120 degree water in there, in theory.

  9. #9
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    Aug 2007
    Location
    Georgia
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    Default Re: Not enough hot water to fill the tub

    I did a quick search and found that 120 degrees at the tap is recomended. It takes 10 minutes of exposure to 120 degree water to cause damage to children. Check and see what your temperature is at the tap. You may need to adjust it. But thats just my opinion. How far of a run is it from the heater to the tub?
    Last edited by tbgworldwide; 12-18-2007 at 10:47 PM. Reason: additional info

  10. #10
    Join Date
    Dec 2007
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    2

    Cool Re: Not enough hot water to fill the tub

    I have a similar problem.
    I just had a new hot water heater installed and I am running out of hot water.
    It is gas.
    It looks like it is installed correctly hot in H and Cold in C.
    The temp is turned way up.
    I do have a recirculator attached which enters through the drain spout at the bottom of the tank.

    Any suggestions is there any way the circulator could cause this?


    They are coming out to switch out tanks today?

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