Why am I running out of hot water??

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by rhliberman, Jan 23, 2008.

  1. rhliberman

    rhliberman New Member

    Joined:
    Oct 6, 2005
    Two years ago we replaced our old, small-capacity water heater with a new 50 gallon GE Smart Water gas water heater. The thermostat is set on the high side - not quite scalding but pretty hot.

    If two people want to take a shower, the second person must wait 30 minutes or so before taking a shower or the hot water will run out before they can finish. Our showers last for about 10 minutes or so.

    From what I know (not very much) water heaters are fairly simple devices; it seems that unless the dip tube is broken, not much else can go wrong. But the unit is two years old so that probably should not be the case.

    Our old water heater had the same problem (not enough hot water) so that is why we got the new one.

    This just does not make any sense. What else can be the problem?
     
    Last edited: Jan 23, 2008
  2. hj

    hj Master Plumber

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    Plumber
    Location:
    Cave Creek, Arizona
    hot water

    Is your home built on a slab with hot water pipes under the floor? IF so, replacing the water heater was probably not the way to solve your problem.
     
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  4. jimbo

    jimbo Plumber

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    Aug 31, 2004
    Location:
    San Diego, CA
    Using the 70% rule, a 50 gallon tank will deliver approximately 35 gallons of water hot enough for a shower. At ~ 2 gallon per minute +,, you get about 17 minutes or less of shower. Check your watch.!
     
  5. rhliberman

    rhliberman New Member

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    Oct 6, 2005
    No, we have a basement. That's where the water heater is located. Thanks
     
  6. rhliberman

    rhliberman New Member

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    Oct 6, 2005
    Very interesting, thanks. I'll start timing our showers. According to GE, a 50 gallon tank is sufficient for a family of four. I guess they think a four minute shower is enough!
     
  7. SteveW

    SteveW DIY Senior Member

    Joined:
    Feb 11, 2005
    Location:
    Omaha, NE
    You can also measure the flow rate of your showerhead - see how long it takes to fill a 1-gallon bucket and do the algebra to figure gallons per minute (GPM) -

    Most new showerheads are rated at 2.5 GPM.

    If you have a showerhead which has a substantially higher flow rate, changing to a 2.5 GPM head would make a lot sense.
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Turn up the thermostat and install a tempering valve. This will give the the equivalent of a bigger WH. The tempering valve mixes cold with the hot from the tank so you don't get scalded, but as a result, your output may be the same temperature, but you're not using as much hot water. Depending on where you live, this can be a much bigger deal in the winter - the incoming water can be signficantly colder which mixes with the hot in the tank.
     
  9. jimbo

    jimbo Plumber

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    Aug 31, 2004
    Location:
    San Diego, CA
    I went to the GE website, and used their calculator..it says for 4 people, 2 bathrooms, a 65 gallon electric would be recommended.
     
  10. Redwood

    Redwood Master Plumber

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    Service Plumber
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    Connecticut
    It looks like a case of GIGO! When it was sized.
     
  11. rhliberman

    rhliberman New Member

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    Oct 6, 2005
    Yes, but running that test is measuring total water flow, not just the hot water - right?
     
  12. Cass

    Cass Plumber

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    Nov 12, 2005
    Location:
    Ohio
    There is more to water heaters than just the stated recovery rate.

    In coming water temp.

    Temp setting at the time on the unit.

    Flow rate on the shower head

    How hot one likes their shower to be.

    Have you checked the actual water temp with a thermometer.
     
    Last edited: Jan 24, 2008
  13. rhliberman

    rhliberman New Member

    Joined:
    Oct 6, 2005
    Our weater heater is gas, but that is a good point you make about the incoming water temperature. However, we experience this problem throughout the entire year. I'm a little confused on the flow rate. Let's say that I turned the water on in the shower at the normal temperature at which I shower, and the flow rate was 3 gallons/minute. Using the 70% rule I saw mentioned previously, since I have a 50 gallon heater that would give me about 35 gallons of available hot water, 3 gallons/minute would give me 10-11 minutes of hot water.

    But, when I measure flow rate it's measuring more than just the hot water because I use a mix when I shower. So, unless I turned only the hot water on at my normal shower pressure the measurement won't be accurate.

    Am I missing something?

    Still, our shower heads are old and probably not as efficient as today's models so they should probably be replaced.

    Thanks!
     
    Last edited: Jan 24, 2008
  14. jimbo

    jimbo Plumber

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    Aug 31, 2004
    Location:
    San Diego, CA
    Manyfactors, as mentioned. Yes, the hotter you set the WH, the higher % of cold you will mix in. But at a reasonable setting of 125º, most folks will be using a very high % of hot in the mix.

    getting back to the basic issue, do you all take long showers? If so, that is the issue. If you say you only take a 5 min. shower, then a 50 gallon tank should do 2 of those, if you are not running a washer or dishwasher at the same time.
     
  15. rhliberman

    rhliberman New Member

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    Oct 6, 2005
    Our showers average between 6 and 7 minutes
     
  16. fidodie

    fidodie New Member

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    new jersey
    Here is a stab: one of the real plumbers could tell you where to look for
    this type problem, or how to isolate it -

    what if there is cross contamination with the cold water somewhere
    else in the house - like a broken backflow preventer, some
    older faucet where the water is mixed at one point, and flow controlled
    at another. acting as a tempering valve as mentioned above, but starting at a
    lower threshold, thus wasting hot by allowing cold water
    into the hot.

    you start out with a hot shower, and consume all the hot water more quickly than expected.
    (i've seen where someone hooked a hot and cold together to feed a dishwasher...
    saving money that way ?)

    I inadvertently had this happen when i installed a new shower at my brother's, and left the test cap on the new shower valve housing, rather than installing the valve.....DIYer learnt something new that day, how to p*off a sister-in-law.

    Other possibility - bad ground strap for the pipes, and it is grounding through the tank, if the dip tube was metal, it would go first? (this just came to mind, i ran a boat in salt water long ago, and worry about that stuff) speaking of salt water, a softener that needs service would add to the problem?

    Do you have di-electric fittings on the tank, and a bonding wire? no wire makes the water do the electrical work (kinda like electro-plating).

    of course if it did it when the tank was new, then the electric angle wouldn't apply.
    Did the problem go away for two years?

    can anyone correlate the symptoms with these possibilities, or let me know if i'm way off base!
     
    Last edited: Jan 24, 2008
  17. ltnicks

    ltnicks New Member

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    Jan 23, 2008
    that was a good read fidodie, I agree to keep it simple. check the thermostat and ensure the drop tube is intact.
     
  18. rhliberman

    rhliberman New Member

    Joined:
    Oct 6, 2005
    I've determined it's a showerhead problem!

    I measured the flow from both showerheads and one of them is flowing at a rate of almost 5 gallons per minute. I'm going to replace the showerhead and see what happens.

    Can somebody recommend a very good basic replacement head which is not too expensive?

    Thanks
     
  19. patrick88

    patrick88 Plumber

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    Sep 3, 2007
    Occupation:
    plumber
    Location:
    Webster Ma.
    For a cheap head goto any store that carries shower heads. The prices go from cheap to very high$$$.

    I run a 50 gal elec. I can take 3 showers with one teen taking 30+ shower. Yes the last shower needs to be quick but not to bad.
     
  20. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Nov 8, 2005
    Occupation:
    Consumer
    Location:
    Hansville, Washington
    Showerhead recommendation

    About 20 years ago I bought a couple of low-flow showerheads for about $10 apiece, and they were great -- 1.2GPM, high-pressure, and a "pause" button for the Navy types. I don't know the brand name, but they look identical to this:

    http://www.treehugger.com/files/2005/10/eco-showerhead.php

    ...and the description fits. Worth $12 (inflation, I guess) just to try, IMHO. If you Google {"real goods" showerhead} you'll find several vendors. One of them calls it their "longtime best-seller", so it may well be the same unit I've got.
     
    Last edited: Jan 30, 2008
  21. Mikebarone

    Mikebarone DIY Senior Member

    Joined:
    Feb 19, 2006
    Location:
    Phoenix, AZ
    How about...

    This is a stab in the dark but, is the larger tank getting enough gas? Maybe the smaller unit you had was rated to get just enough gas, for a smaller tank?
     
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