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  • Water heater size - jet tub

    Need your wisdom.... About 2 years ago I (HD) replaced my water heater because the original one blew out of the bottom and flooded my basement. The largest size I could get on short notice was a 50 gal GE and is the same size as the old one. The problem is that we have a 2 person jet tub that we use to be able to fill with hot water from the old water heater but cannot fill more than 1/3 with the new heater before running out of hot water. We would love to start using the tub again.

    P.S.

    There are no other hot water draws happening at this time.

    Any thoughts?

  • #2
    Re: Water heater size - jet tub

    Originally posted by osgoor View Post
    Need your wisdom.... About 2 years ago I (HD) replaced my water heater because the original one blew out of the bottom and flooded my basement. The largest size I could get on short notice was a 50 gal GE and is the same size as the old one. The problem is that we have a 2 person jet tub that we use to be able to fill with hot water from the old water heater but cannot fill more than 1/3 with the new heater before running out of hot water. We would love to start using the tub again.

    P.S.

    There are no other hot water draws happening at this time.

    Any thoughts?
    When you say the new heater is the same size as the old heater, does it have the same BTU rating and first hour recovery as well? Gallons is just about storage not capacity per say.

    Mark
    "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

    I never lost a cent on the jobs I didn't get!

    Comment


    • #3
      Re: Water heater size - jet tub

      That's a very good point. Since the old one is long gone I would not be able to compare them. What would be acceptable values to look for to handle the task I asked about.

      Thanks for the input.

      Comment


      • #4
        Re: Water heater size - jet tub

        Originally posted by osgoor View Post
        That's a very good point. Since the old one is long gone I would not be able to compare them. What would be acceptable values to look for to handle the task I asked about.

        Thanks for the input.
        You should be able to look at the label on you water heater to see what the BTU rating is. I'm guessing it is 40,000 BTU with a recovery rate of 42 gallons per hour. To show you how much things can differ, one manufacturer has a line where the 50 gallon heaters start at 40,000 BTU with a recovery of 40.5 gallons per hour all the way to 65.000 BTU with a recovery of 66.5 gallons. Then if you go to their high efficiency model you can go all the way to 199,000 BTU with a recovery of 257 gallons. All of the above are 50 gallon water heaters.

        Sizing your water heater would be tough online and hiring a licensed plumber would be your best bet. However, if you really are going to do it yourself a good start would be to figure out the capacity of your jetted tub and what temperature you would like to maintain the water.

        Mark
        "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

        I never lost a cent on the jobs I didn't get!

        Comment


        • #5
          Re: Water heater size - jet tub

          How much does the recovery rate really matter in this application though? The tub will be filled in something like 10 minutes, so going from a 40 gallon recovery to a 200 gallon recovery will only result in an additional 27 gallons of water assuming everything is ideal, and I suspect things are less than ideal in practice.

          I had a 40 gallon indirect tank with ~200 gallon recovery, and it wouldn't get the tub more than half filled. With an 80 gallon tank (same boiler so same recovery), everything is great and I never run out of hot water.

          Comment


          • #6
            Re: Water heater size - jet tub

            Originally posted by cpw View Post
            How much does the recovery rate really matter in this application though? The tub will be filled in something like 10 minutes, so going from a 40 gallon recovery to a 200 gallon recovery will only result in an additional 27 gallons of water assuming everything is ideal, and I suspect things are less than ideal in practice.

            I had a 40 gallon indirect tank with ~200 gallon recovery, and it wouldn't get the tub more than half filled. With an 80 gallon tank (same boiler so same recovery), everything is great and I never run out of hot water.
            It really depends on the size of the tub. If your tub has a 100 gallon capacity it would take 20 minutes at 5 gallons per minute to fill. The fact that it takes so long to fill also means you are losing hot water while it fills. Assuming there is no where to install a larger tank the high recovery may help. On our jetted tub we have an in line heater which helps to maintain the temperature but in many tubs the user has to add hot water to it after they have been in the tub for a bit.

            Mark
            "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

            I never lost a cent on the jobs I didn't get!

            Comment


            • #7
              Re: Water heater size - jet tub

              Thanks for the comments. I am not thinking of changing the heater myself but I was wanting to know the possible reasons that it is unable to do the job and if someday I want to spend the money to fix it I'll at least know what to look for.

              Comment


              • #8
                Re: Water heater size - jet tub

                Originally posted by osgoor View Post
                Thanks for the comments. I am not thinking of changing the heater myself but I was wanting to know the possible reasons that it is unable to do the job and if someday I want to spend the money to fix it I'll at least know what to look for.

                Keep in mind the above only addresses sizing issues. It is possible your new heater is not operating properly. If you can figure out the GPM at the spout you should be able to test the first hour supply.

                Mark
                "Somewhere a Village is Missing Twelve Idiots!" - Casey Anthony

                I never lost a cent on the jobs I didn't get!

                Comment


                • #9
                  Re: Water heater size - jet tub

                  I'm guessing your old WH was probably set a higher temperature allowing you to fill the tub higher. To make things simple I would just add a second 50 gal WH in series. Might be more beneficial to just add a 50 gallon storage tank and a recirculation pump. This will give you more than enough hot water to fill any tub.
                  Distractions are everywhere, don't lose sight of your dream.

                  Comment


                  • #10
                    Re: Water heater size - jet tub

                    Rheem makes a 50 gal 65000 BTU heater.In the Mpls area call *Water Heaters Only*.
                    They have access to many charts and water heater specs.
                    Be ready to answer many questions about your hot water usage and they can fit a heater to work well for all you could then throw at it.
                    Then have a licensed professional install and have inspected.
                    Happy new year and good luck.
                    Last edited by Jay Mpls; 12-29-2008, 11:22 PM. Reason: I spell like hell.

                    Comment


                    • #11
                      Re: Water heater size - jet tub

                      The need to fill a large tub is one of the few applications where, in my opinion, a tankless WH makes sense. Would need to be a model with a large capacity....at least 7 GPM at 70ยบ rise. But if you need plan to use the big tub often, the very high initial cost of the tankless may be worth it.

                      Comment


                      • #12
                        Re: Water heater size - jet tub

                        Thanks for all the advice. It would be nice to use the tub once in awhile but we would only use it 6 - 10 times a year so the cost does not seem worth it. We also do not plan on being in our current home for a long time (economy depending). Thanks again for all the input.

                        Comment


                        • #13
                          Re: Water heater size - jet tub

                          as mark mentioned, the heater might be off.

                          set the temperature to 130. calibrate a 5 gallon bucket.

                          get an instant read thermometer.

                          fill the bucket and add the results of all buckets that are 100 or higher.

                          you should produce 35 gallons/ 7 buckets. a storage type residential heater should produce 70% of usable hot water.

                          it could be a dip tube issue. it could be extremely cold water coming in and blending with the not so hot water.

                          first hour rating is fine for recovery, but not feasible for filling a tub in 1 shot. assuming a standard 40,000 btu heater.

                          too bad you don't have the specs on the old heater.

                          do the draw/ bucket test and post your results. need starting temperature and ending temp. along with cold water temp

                          rick.
                          phoebe it is

                          Comment


                          • #14
                            Re: Water heater size - jet tub

                            I've got an indirect in my house, but to boost the capacity I raise the temp to 140 degrees and put a mixing valve at the tank. I've never run out but then again there different animals. The mixing valve will only give you another 10-15%.

                            How about you just put some more people in the tub with you? It will raise the water level.

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