Running out of hot water

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by cjc, Mar 12, 2005.

  1. cjc

    cjc New Member

    Messages:
    7
    Location:
    Wisconsin
    I have a 40 gallon Rheem power vented gas water heater. When two people in the house take consecutive showers, the second person runs out of hot water. We recently purchased the house so we aren't sure how long the problem has persisted. The house and water heater are only 7 years old.

    The thermostat on the water heater is set at medium which says its the equivalent of 125 degrees. I ran hot water from a faucet over a thermometer for a couple minutes and I get a reading of 115. We do seem to have excellent water pressure. Could this be part of the problem? Could it be that the pressure is too good? If so, is there a way to adjust it??

    I did do a test to see how much water comes out of the shower head in one minute. After a minute we had approximately 4 gallons of water in a bucket. Could this be the culprit??

    I have also considered draining the water heater in case there is sediment build-up. The problem is that the drain valve is plastic and has a large chip out of it, so I don't think I can connect a hose to it. Can this be replaced without making a mess?

    Any suggestions to these questions would be greatly appreciated.

    Thanks,

    cjc
  2. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,382
    Location:
    Yakima WA
    I have a Rheem power vent heater that acted much the same. I found the burner was not igniting when it was supposed to. The vent fan would kick on, but no flame. I explored the Rheem website and got some clues as to the problem. It was the ignition module. I replaced it myself for $65. End of story. You can get the module from Rheem, but it's around $100 plus shipping from them. They suggested I find a plumbing supply house locally, which I did. If you open the door over the controls, you will see a black box on the upper part of the enclosure. That's it. Easy to change. Replacing the hose bib on the drain is easy, but you do have to drain the tank. Draining the tank won't help or hurt you problem, but it is good maintainance to do that about once a year. Test the TP valve then, too. Water pressure has nothing to do with the problem either. When the tank is lighting off properly, you should be able to shower, wash clothes, and disher without running out of water. I don't think you could expect to run hot water full stream all day and not run out, but just regular usage should present no problems.
  3. cjc

    cjc New Member

    Messages:
    7
    Location:
    Wisconsin
    Thanks for the input, Gary. Is there any way to test to see if indeed it is the ignition module, or do I just wait for the vent fan to kick on and check for a flame??

    thanks again,

    cjc
  4. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,019
    Location:
    Cave Creek, Arizona
    wh

    At 115 degrees when you take a "hot" shower you probably have to use all hot water so you will only get about 30 gallons of hot water, and maybe less because the incoming cold water will be cooling the stored water's tempefature. At 140 degrees, you would have to introduce cold water to make the shower water comfortable, and that would increase the effective capacity of the tank to 50 and possibly 60 gallons.
  5. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,382
    Location:
    Yakima WA
    I'm sure there is a way to test it with a volt meter, but the information from the Rheem website made it pretty clear what the problem was. Just draw enough quanity to hot water to make the fan come on. If you have the access door open, you will probably notice yellow flame. If that yellow flame does not turn blue, you're ignitor is not functioning. Mine was sporatic for awhile, gradually worsening until I was spurred into fixing it.
  6. SteveW

    SteveW DIY Senior Member

    Messages:
    1,052
    Location:
    Omaha, NE


    I'm with hj -- if you're using 4 gallons/minute and take a 10-minute shower, and if the hot water is coming out at 115 degrees, you are using mostly hot water for your shower and thus nearly depleting your 40-gallon water heater tank.

    If I were you, I'd:
    1) increase the temperature at the water heater a bit -- try to get to at least 120 (which is the minimum temp for hot water for your dishwasher, unless it has an integral heater of its own);

    and

    2) switch to a lower-gallonage shower head.
  7. Turn it up "at your own risk"

    your power vent unit is probably working just fine...

    If the temp is at 115, especially if you live in a colder region, it just simply isnt hot enough to maintain the demand....the cold water comes into the unit and the temp crashes too quickly, its called "stratification".. thats stra---ti--fi-- ca--tion. Ice cold water comming into a tank and mixing with the hot water , making the overall temp to crash dramatically.

    Do you realize that you can literally pee a stream from your own body that can hit 105 during a bad fever??? Thiink about it..... if you got really sick your pee temp might even go higher. (you might die too)

    So 115 is literally only barely above luke warm. -- pee water.
    How can you expect the water heater to keep up when its set on "pee water"

    I had a 40 gal gas and it was the same story...
    unless you have small helpless babies in the house , or elderly people,
    only a total moron is going to ever scald themselves.

    We have 2 kids in our house 4+ 7 yrs old and I have my 50 gal Smith unit set on high. I know the risk, and we have a whirlpool too. It really is not much of a problem, though once in a while I will get a hot rush while doing dishes.
    Thats a small trade off..
    -------------------------------------------------------------------------
    We have become a law suite happy country ever since that one old lady spilled hot coffe in her crotch at McDonalds and got 3 mil. for it. ( its still being appealed, so she hasnt ever got the money yet )

    and now its in everyones mind to worry about things like this ...

    Rheem has all those warning labels on the unit to protect themselves from the next skumbag lawyer who tries to sue them....its just a frivouls lawsuit, it ties up the courts, but it cost everyone money.

    Simply turn it up a little bit at a time -- "at your own risk" -- and see if the problem doesent just go away.

    Or play it safe and spend about 970+ for a 50 gallon power vent and leave it set on "low"

    good luck.
    Last edited: Mar 13, 2005
  8. SteveW

    SteveW DIY Senior Member

    Messages:
    1,052
    Location:
    Omaha, NE
    Shower head

    Forgot to mention my personal preference for a low-gallonage showerhead: Revolution by Moen. It's 2.5 gpm but you don't notice the decrease in water flow because it kind of spins the water drops as they leave the head -- feels like a gentle, warm rain...
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