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Thread: Not enough hot water

  1. #1
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    Default Not enough hot water

    Attempted to search for a similar issue and didn't find anything, I apologize if this has been brought up before.

    I moved into a house with a 1996 Kenmore 40 gallon gas water heater. I was going to take a shower but discovered there was no hot water, although after running the water for awhile the burner did turn on and provide hot water. Even though we now had hot water it did not last very long, we barley had enough for one shower, we would have to continually turn the hot water up during the shower before it it would get cold. I did check water heater temperature and it was set between low and hot so I turned it up to hot (which was the middle setting). This seemed to provide hot water when we needed without running the water first but there still was not enough for a full shower. After some research I thought the problem might be the dip tube so I had a repair man come out (FYI, though our home warranty company). He didn't think it was the dip tube because a broken dip tube would cause the water to suddenly go cold which didn't seem to be our case. He did turn the thermostat all the way to the hottest setting, Very Hot. Now the water is extremely hot (too hot in my opinion), when taking a shower we get a little longer shower but will still run out of hot water during a longer shower and we still have to continually increase the faucet temperature. The repair man did recommend draining the tank which we stated to do but after filling 2 five gallon buckets the water was clear and there was nothing in the water so I stopped. tI just doesn't seem right that the temperature doesn't say the same though the whole shower.

    Our apartment had a small electric water heater, I'm assuming it was about half the size of our current and we never had a problem getting though full show, maybe the 2nd shower would require the temperature to be increased we didn't completely loose all hot water

    I'm hoping someone can give me a better idea of what the problem might be so I know if the repair person is correctly addressing the issue.

  2. #2
    Plumber Cass's Avatar
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    Call the warrenty company back and tell them you need to have the unit fixed or replaced...that is how it works...the unit is not working right and it is the responsibility of the warrenty company to get it to work right...if the problem can't be fixed they will replace it...I am 99% sure that it is the dip tube...but getting a new heater would be far better for the $$$ spent...

    Just tell them to fix it or replace it...it is not sedement build up causing the problem...if there were that much sediment buildup causing the problem you wouldn't be able to drain it...
    Last edited by Cass; 11-30-2009 at 04:55 AM.

  3. #3
    Master Plumber Redwood's Avatar
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    Better yet tell them that the initial blast of water is scalding hot and you are worried about getting burned...

    Maybe fear of a multi million dollar judgement will stir them into action...

    I agree with Cass...

    There is little doubt in my mind the diptube is defective.

    Can you give us the water heater serial number?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    The whole idea of the dip tube is to direct the incoming cold water towards the bottom of the heater. Since warm water is lighter, it naturally gravitates to the top. If the dip tube fails, the cold doesn't magically immediately cross over to the hot outlet, it still mixes with the hot water that is in the tank, so it would more quickly cool off. It sure sounds like the dip tube is shot. Now, marathon showers will almost always deplete a tank type WH. A big indirect might be able to keep up with a shower as can some of the bigger gas units, but the more typical ones will not provide continuous hot water.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member Runs with bison's Avatar
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    Sounds like the dip tube. But regardless this is not normal and the home warranty company is on the hook for fixing it. With my recent/now expired home warranty initiating a call/claim was $75 so at the point you are I would already have that much into it...and I would expect it to be fixed if I paid them a thin dime.

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    Thanks everyone, this has been very helpful. So far I have not had any problems with the warranty company or the repair person, I just want to be proactive with dealing with this issue. Someone is coming out on Monday so hopefully he will get this fixed.

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    Master Plumber Redwood's Avatar
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    Quote Originally Posted by goldie View Post
    So far I have not had any problems with the warranty company or the repair person,
    We understand...
    It's just many of us have a low level of confidence in home warranty companies and their vendors...

  8. #8
    DIY Member WorthFlorida's Avatar
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    I hope the ding-dong that raised up the temp to max is fired and lose his license. Almost all states have laws that water heaters cannot be set at no more than 110 or 120 degrees. If he shows up I wouldn't let him back in the home.

    A water heater set to the max can be up to 150 degrees. I recently lower one in a rental property after I nearly burned myself washing my hands. Using a thermometer it was at 145 degrees. Read about degree burns @ http://en.wikipedia.org/wiki/Burn

    A quote from the consumer product safety council.
    "Most adults will suffer third-degree burns if exposed to 150 degree water for two seconds. Burns will also occur with a six-second exposure to 140 degree water or with a thirty second exposure to 130 degree water. Even if the temperature is 120 degrees, a five minute exposure could result in third-degree burns."

    Tap Water Scalds
    http://www.cpsc.gov/CPSCPUB/PUBS/5098.html

    http://www.tap-water-burn.com/
    Last edited by WorthFlorida; 12-02-2009 at 08:44 PM.

  9. #9
    Homeowner Thatguy's Avatar
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    Quote Originally Posted by goldie View Post
    a 1996 Kenmore 40 gallon gas water heater.
    we would have to continually turn the hot water up during the shower before it it would get cold
    40% get replaced this early. If you fix it you have even odds of getting another four years out of this unit.

    A 25 gallon shower only uses ~16 gallons of hot water.

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    Update, the repair man came over today, he measured the hot water from our bathtub. Turned the water on to the highest/hottest setting, measured 137 degrees at the beginning and 100 after 11 minutes. He called the warranty company and said the water heater is fine. From the numbers provided is this normal? Obviously something is wrong since we can only get one shower in but mathematically does this make since?

    If anything I'll recheck the numbers tonight or tomorrow morning since I had just taken a should an hour before he came, so the tank would have been just been refilled and reheated I assume.

    The serial number is E98552147.

    Thanks everyone for you input so far, this forum has a ton of great information!
    Last edited by goldie; 12-07-2009 at 08:30 AM.

  11. #11
    Homeowner Thatguy's Avatar
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    A normal shower is 90F to 110F.

  12. #12
    In the trades Dana's Avatar
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    Quote Originally Posted by Thatguy View Post
    A normal shower is 90F to 110F.
    90F showers are NORMAL!?!

    (Maybe when the ol' lady has a headache it is... )

    ~105-ish is more typical. Anything between a bit above body temp (100F) and 110F is tolerable, but under ~99F is tepid to active-cooling.

  13. #13
    DIY Senior Member Runs with bison's Avatar
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    Quote Originally Posted by goldie View Post
    Update, the repair man came over today, he measured the hot water from our bathtub. Turned the water on to the highest/hottest setting, measured 137 degrees at the beginning and 100 after 11 minutes. He called the warranty company and said the water heater is fine. From the numbers provided is this normal? Obviously something is wrong since we can only get one shower in but mathematically does this make since?
    Flowrates, flowrates, flowrates. The information is meaningless without your shower flow or the tub flowrate at the measured conditions. We need an idea of how much water passed before it cooled.

    What flowrate did he measure? The 11 minutes is meaningless without a flowrate. If it is ~4 gpm then he is probably correct...assuming that the drop to 100 F doesn't occur in the first 7 minutes or so. It should remain very hot for the first 5 at that flowrate. What is the incoming cold water temp? This latter bit will give some idea how much rise the system experiences.

    Max temp on my unit appears to be about 160 F on the dial. Starting at only 137 F at the max setting would indicate a problem if that is where it is at (assuming it had time to recover.) However, if the tub supply valve is one with the built in tempering limitations 137 might be all it will ever show. At the max setting and with a properly working dip tube the burner should fire reasonably soon from a high flowrate. I don't know how much delta is built into them.

    So my advice is to measure the flow rate of hot only in the tub and shower. Then you have a way to make some sense of the numbers.

    If you are using a 5 gpm (or higher) showerhead and have a 40 gallon tank then you are likely to have the sort of problems you've described even with a 10 minute shower. I wouldn't expect any problem with a standard 2.5 gpm showerhead and a 40 gallon tank in a 10 minute or less shower.

    How long are your typical showers? My wife is the long shower taker in the household (plus she runs the shower hotter.) The rest of us take about 7 mins. on average. I've measured the shower temp I prefer as about 105 F. Back when we had a 5 gpm showerhead in another home my wife could run the tank out so I would shower first.

    If you take long or high flowrate showers then you probably want a 50 gallon tank when replacement time comes around.

  14. #14
    Retired Defense Industry Engineer jadnashua's Avatar
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    At high flow rates, you'll likely only get aout 70% of the volume of the tank before you notice it starting to cool off, so as said, without volume numbers, the test done was meaningless. At lower flow rates, the burner (or element on electric) can help sustain the output, but eventually, you overcome that if the flow is high enough.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  15. #15
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    I just measured the flow rate at 5 GPM from the bath tub, not shower. So, starting at 137 degrees the water temp dropped to 100 degrees after 11 minutes at 5 GPM. I measured the flow rate of our shower head to be around 2.5 GPM.

    What doesn't make sense is that 1.5 hours before the repairman came I took a 7 minute shower, although I didn't run out of water I had to turn up the temp during the shower. I'm guessing I had another 3 minutes before I would have run out of hot water. If I'm correct, our numbers are not adding up because I'm not using 137 degree water.

    This is making less and less sense as the post goes on. All I know is my wife and I could get though 2 showers with a small water heater in our apartment, I'm guessing it was 20-30 gal. Also when I lived with my parents there were 3 teenagers and 2 adults with a 40 gal tank and never has major problems with hot water.

    I need numbers to back this up but it seems like if the hot water isn't used for 10 or 12 hours it doesn't last as long as it might if hot water was used 1 hour ago.

    I'll do some testing in the morning, I just wanted to post my thoughts before I went to bed. Thanks everyone!
    Last edited by goldie; 12-07-2009 at 09:00 PM.

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