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  1. #1
    Join Date
    Jan 2013
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    Default Increase Hot Water Capacity

    I have a relatively new home (2004), with a 55 gallon hot water heater. We recently completed a bathroom remodel, which includes a spa shower and an extra large bath tub. Unfortunately our hot water heater cannot keep up with the increased demand. Is there a way to improve our hot water capacity so we can enjoy the new bathroom features? Are the tankless water heaters effective and worth the investment? Should we move to a larger water heater tank? Is it possible to have a combination of both (tankless+tank)?

  2. #2
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    Jul 2010
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    Default Re: Increase Hot Water Capacity

    The easiest way is to install a larger water heater. If your 55 gal unit is older than 8 years, this is your best option.

    However, it really depends on how frequently you use the spa.

    Other options:

    - Add a water heater, 30 - 40 gal. Not too expensive and will work for you.
    - Tankless water heater. Expensive installation, but could work for you.

  3. #3
    Join Date
    Jul 2009
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    137

    Default Re: Increase Hot Water Capacity

    anthony,

    If you happen to have hot water heat (radiators, baseboard,etc.) it is usually possible to attach a 40 gallon indirect hot water heater that will provide an economical way to supply hot water to the spa.

    Is your present HWH electric? Do you have natural gas heat? Fuel Oil? Forced Air Furnace?, Propane?
    Last edited by Pelton; 01-26-2013 at 01:05 PM.

  4. #4
    Join Date
    Sep 2012
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    Boston
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    Default Re: Increase Hot Water Capacity

    i like dj's idea. if your heater is over 8 or so years old it would make sense to look into a larger or indirect system. if it's not you can add a second water heater.

  5. #5
    Join Date
    Dec 2007
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    Tennessee
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    Default Re: Increase Hot Water Capacity

    The simplest thing to do is to turn up the temperature of the water heater. If you're not getting enough hot water, then I'd suspect that your WH is set to around 120. If you raise it to 140, you will be mixing more cold water in to make the water temp at the tap just right so it will last longer.

    You could go even higher if needed. I'd recommend that you go up in 10 increments until you find the minimum temp to meet your needs. Be aware that if you have small children, the higher the temperature, the greater the risk for scalding from teh sink faucets if they are not careful.

    To help save energy costs, make sure your hot water pipes are insulated and you might even consider an insulation blanket on the water heater itself.

  6. #6
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    Default Re: Increase Hot Water Capacity

    Quote Originally Posted by keith3267 View Post
    The simplest thing to do is to turn up the temperature of the water heater. If you're not getting enough hot water, then I'd suspect that your WH is set to around 120. If you raise it to 140, you will be mixing more cold water in to make the water temp at the tap just right so it will last longer.

    You could go even higher if needed. I'd recommend that you go up in 10 increments until you find the minimum temp to meet your needs. Be aware that if you have small children, the higher the temperature, the greater the risk for scalding from teh sink faucets if they are not careful.

    To help save energy costs, make sure your hot water pipes are insulated and you might even consider an insulation blanket on the water heater itself.
    The OP doesn't need hotter water, he needs more hot water to fill a spa.

    A thermostat set higher will result in a burner working overtime even when he doesn't use the spa.
    Last edited by dj1; 01-27-2013 at 10:44 AM.

  7. #7
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    Dec 2010
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    Houston Texas
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    Default Re: Increase Hot Water Capacity

    A tub that heats the water is best as the water already in the tub can be re-warmed.

    Bain Ultra makes tubs that heat the water

  8. #8
    Join Date
    Dec 2007
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    Tennessee
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    Default Re: Increase Hot Water Capacity

    Quote Originally Posted by dj1 View Post
    The OP doesn't need hotter water, he needs more hot water to fill a spa.

    A thermostat set higher will result in a burner working overtime even when he doesn't use the spa.
    Sorry but I have to strongly disagree with you on BOTH counts. Bath water will be hot at 91-93 Thats about 35 higher than water coming in on the clod water pipe. Now a % of heat coming into the bathtub will be lost to the tub itself so that will cool the hot water some. How much ill depend on the tub materials, size and other factors.

    For the sake of this post, lets say that water at the faucet at 98 will be sufficient after heat loss to the tub to provide a hot bath. That will be 40 to 45 above the cold water. To achieve the 98 faucet temp, cold water will be mixed with water from the water heater. Raising the temperature of the water heater will mean that more cold water will get mixed with the hot water to achieve the desired temperature, effectively yielding more water at the desired temperature.

    For example, if the spa tub is 120 gallons and the cold water is 58, then 65 gallons of cold water would be mixed with 55 gallons of hot water @ 145 will provide the desired bath water. It maybe necessary to raise the temperature in the hot water heater by another 5 to 10 to compensate for heat loss in the pipes, depending on distance and insulation level of the hot water pipes.

    Same example but with an 80 gallon water heater, 40 gallons of cold water will be mixed with 80 gallons of hot water @ 118 for the desired bath water. Again you have to add 5-10 for the heat loss in the pipes.

    As for the burners, it takes the same number of BTU's to heat 120 gallons of water to 98 no matter whether its dome in a smaller or larger water heater. Hot water maintenance cost should be pretty close, i.e maintaining 80 gallons @125 or 55 gallons @ 150.

    The big advantage to the 80 gallon water heater is lower water temperature at the tap in case a small child turns on the hot only and puts his or her hands into it. The lower temperature will reduce the chances of scalding. The larger water heater is safer in that respect. I never said that turning up the temperature was teh best choice, just the simplest.

  9. #9
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    Default Re: Increase Hot Water Capacity

    Let me offer one more option, you can use this bathroom Japanese style. In Japan, tubs are used only for soaking, you never take soap into the tub. Now when you use the tub, you first take a shower to clean up. Then you let half the water out from the previous use. The remaining water will be at room temp, say 68. You could refill the tub with 55 gallons of 140 water to achieve the desired bath temperature, and you save water too. Just don't stay in the shower too long.

    When they shower in Japan, they wet down, turn off the water, soap and scrub, then turn the water back on to rinse. That doesn't use very much water.

  10. #10
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    Default Re: Increase Hot Water Capacity

    I agree with Keith. You will get more hot water by raising the temperature on the heater. The problem of scalding water as dj1 mentioned can be serious. But that can be solved by install a tempering valve at the water heater.

    John

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