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  • Hot water piping and heat loss

    Say I have the following plumbing:

    S-----------|
    S-----------|---------H

    H = Hot water heater, S = Sink

    Say time has passed and the water in the piping is cool.

    Say I turn the hot on the bottom sink, will I lose water heat as the water passes the split in the piping to the top sink as a result of convection?

    Will I continue to lose water heat until the water in the top sink's piping has caught up in temperature?

    This is more plumbing "theory" type question.

    Thanks ...
    Last edited by theoak; 09-04-2008, 09:17 PM.

  • #2
    Re: Hot water piping and heat loss

    Wait wait wait, In order to answer your question I first have to know,

    Are we talking plumbing theory or plumping theory?
    West Trail Mechanical Ltd
    Service. Commitment. Expertise.

    www.westtrailmechanical.ca

    Comment


    • #3
      Re: Hot water piping and heat loss

      Very little. Some heat will travel, but for the most part it won't unless it has another route it can travel to circulate. When you shut off the faucet, and the water heater starts reheating, you would at that time notice more heat travel up that pipe, because of expansion that is going on.

      Duck, is this wrong?
      sigpic3:00, I mean 5:00, and work is done. Time to crack a cold one.

      Comment


      • #4
        Re: Hot water piping and heat loss

        Do you have a tankless problem?

        J.C.

        Comment


        • #5
          Re: Hot water piping and heat loss

          Originally posted by bigPipe09 View Post
          Wait wait wait, In order to answer your question I first have to know,

          Are we talking plumbing theory or plumping theory?
          He he ... fixed

          Comment


          • #6
            Re: Hot water piping and heat loss

            Originally posted by JCsPlumbing View Post
            Do you have a tankless problem?

            J.C.
            Feeling a little defensive are we

            No ... just got thinking with all this heat going around in my pipes ... how things would behave ...

            ( Really ... the question could apply to a tank just as easy as a tankless or any other hot water source for that matter ... hmmm ... maybe I am getting a little defensive now )

            Comment


            • #7
              Re: Hot water piping and heat loss

              Originally posted by theoak View Post
              Say I have the following plumbing:

              S-----------|
              S-----------|---------H

              H = Hot water heater, S = Sink

              Say time has passed and the water in the piping is cool.

              Say I turn the hot on the bottom sink, will I lose water heat as the water passes the split in the piping to the top sink as a result of convection?

              Will I continue to lose water heat until the water in the top sink's piping has caught up in temperature?

              This is more plumbing "theory" type question.

              Thanks ...
              In a word, yes and no.

              YES in that you will continue to lose heat as long as the water is flowing past this point. BTUs will be lost (transmitted through convection) into the risers' static water and pipe mass. There will be BTUs lost (conducted up the riser and radiated out into the room) at some rate but it will be relative to ambient temperature, insulation presence (if any), etc.

              And NO once the flow stops because eventually the temperature will equalize. How far the heat loss will conduct will depend on a number of factors just as in the above condition. Insulation quality/thickness (if any), ambient temperature, length of riser, etc.

              Can that amount be calculated? YES, if you know the pipe material and size, insulation values, water temp at the branch connection, ambient temperature, and other variables relative to your installation.

              Is it worth doing? NO, not unless your energy budget is so tight that you need to account for every BTU.
              ---------------
              Light is faster than sound. That's why some people seem really bright until you hear them speak.
              ---------------
              “If I had my life to live over again, I'd be a plumber.” - Albert Einstein
              ---------
              "Its a table saw.... Do you know where your fingers are?"
              ---------
              sigpic http://www.helmetstohardhats.com/

              Comment


              • #8
                Re: Hot water piping and heat loss

                So thinking out loud ...

                Would it be better then to run your hot water piping from the top of the home and then drop lines down to your appliances? (A top down approach.)

                A lot of homes seem to run their plumbing in the crawl space underneath the home and then up to the appliances. (A bottom up approach)

                Due to the fact that hot water rises, you would be inclined then to lose more hot water with a bottom up approach via convection?

                Granted, as noted above, you might be splitting hairs, but would it be "best practice" then to go top down if you can?

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                • #9
                  Re: Hot water piping and heat loss

                  So what exactly do you do on 'computers'? Are you engineering your next house? Pulte believes in the top down approach. So does Allen Ethan. I prefer my W/H in the basement, preferably where it doesn't have to be dragged accross the carpet to replace it.
                  sigpic3:00, I mean 5:00, and work is done. Time to crack a cold one.

                  Comment


                  • #10
                    Re: Hot water piping and heat loss

                    Originally posted by boillerman View Post
                    So what exactly do you do on 'computers'? Are you engineering your next house? Pulte believes in the top down approach. So does Allen Ethan. I prefer my W/H in the basement, preferably where it doesn't have to be dragged accross the carpet to replace it.
                    I work with CRM (Customer Relationship Management) applications.

                    No, I am not engineering my next house. Would not know where to start

                    I did just install a tankless water heater though ... hence my recent interest in plumbing.

                    I am also adding on a bathroom onto my house. The other day I was looking at the plumbing and noticed that the plumber went "top down". I was expecting him to go "bottom up". Which led to further thinking that knowing that hot water rises, would top down be better?

                    Hence the questions ...

                    Comment


                    • #11
                      Re: Hot water piping and heat loss

                      Originally posted by theoak View Post
                      I work with CRM (Customer Relationship Management) applications.

                      No, I am not engineering my next house. Would not know where to start

                      I did just install a tankless water heater though ... hence my recent interest in plumbing.

                      I am also adding on a bathroom onto my house. The other day I was looking at the plumbing and noticed that the plumber went "top down". I was expecting him to go "bottom up". Which led to further thinking that knowing that hot water rises, would top down be better?

                      Hence the questions ...
                      We usually run whatever is the most convenient way to get from point A to point B without having to bury lines under cement. Hopefully.
                      sigpic3:00, I mean 5:00, and work is done. Time to crack a cold one.

                      Comment


                      • #12
                        Re: Hot water piping and heat loss

                        Originally posted by boillerman View Post
                        We usually run whatever is the most convenient way to get from point A to point B without having to bury lines under cement. Hopefully.
                        That is what I figured, and in the end it probably does not make a difference, but I was just wondering if there was a "best practice" concerning plumbing.

                        My question has been answered.

                        Thanks all for your input.

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