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Heating Water from FLU - Forno Bravo Forum: The Wood-Fired Oven Community


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Heating Water from FLU

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  • Heating Water from FLU

    Hi All.

    I have moved house and had to leave my beautiful WFO behind (nickenamed the "Old Girl").

    Good news is I get to build another one in our new house, cannot wait to get started.

    I was wondering if anyone has had any experience in wrapping copper pipe around the flu to heat up water from a garden tap? I am planning on having a sink next to my new oven and like the idea of heating water for dishes, cleaning etc (to be honest I just like the challenge).

    Look forward to hearing if anyone has had some success with this.

    Last edited by pizzahead; 06-30-2011, 09:20 PM.

  • #2
    Re: Heating Water from FLU

    There was a recent thread on this topic:


    Seems like a bad idea to me. A simple solar collector seems like a better plan.

    And to your specific question, I'm not aware of anyone who has tried this, at least that's reported back to the forum.
    My geodesic oven project: part 1, part 2


    • #3
      Re: Heating Water from FLU

      If it is in any way going to be a pressurized system don't do it (unless you are a boiler engineer).


      • #4
        Re: Heating Water from FLU

        Hi Neil. No pressurized system intended, I dont want to blow myself (and my oven) up. I intend on fitting off a copper pipe to a garden tap. When you turn on the tap the copper pipe (wrapped around the flu) fills with water, is heated and then is directed to the sink next to the oven. It would be my version of "instant hot water". There will be no water cylinder full of hot water. Your thoughts?


        • #5
          Re: Heating Water from FLU

          Still sounds like a lot of effort for something that can be achieved in a safer/more efficient way.

          1 - run water from your house.
          2 - get an instant hot water setup. (there is a thread around somewhere)


          • #6
            Re: Heating Water from FLU

            I figure it would be pretty simple to wrap the pipe around the flu prior to insulation/render and have water coming in one end cold and out the other hot. I am really only doing it becuase it can be done, I realise there are other more efficient ways to get hot water to an outside sink but like the idea of using the otherwise wasted heat from the flu.



            • #7
              Re: Heating Water from FLU

              Hi Guys/Girls,

              I just joined, and it's a fantastic site.

              I was involved in testing gas appliances for many years, and the concept of using a coil in a chimney is sound provided you have the system vented and ideally with water continually in the coil. This is what they do in the outback, but with a vented storage tank in the roof cavity and utilising a header tank.

              Having a vented tank is probably the best option.

              However, if you choose not to have a tank, keep the coil as far away from the hottest part of the actual flueway as practical, whilst letting the water absorb only a fraction of the possible heat from the flueway. ie instead of having boiling water come out the end of the coil, aim for a temperature rise of say 20oC above ambient. Additionally, for safety, a PTR valve would be a good idea somewhere in the system.

              Hope this helps.


              • #8
                Re: Heating Water from FLU

                if you put oven onto a out door tap , this is a closed pipe because its on to the mains water system so when you turn water on it goes into a 100 200 300 or even a 400degre copper pipe around your oven. it will flash boil and steam needs to get out some where and fast . steam burns just like fire and boiling tar .. also if you only have water in it some time the pipe will corrode and you will get green water. i have spoke to a plumber he said he is very interested in this thinks it a good idea but wood want to see the oven setup working to figure out how many pressure valves would be needed and where to put them ,, but said defo need to be an open vented system . you can not just put water in it when you feel like . hope this helps a little in your hunt for hot water. stick a pot of water into the oven to wash up


                • #9
                  Re: Heating Water from FLU

                  Why not connect a train whistle up to the pressure valve and you would have the most unique dinner bell in town.



                  • #10
                    Re: Heating Water from FLU

                    One idea we talked about a while back in another thread that I liked was using an open top system. I made up a quick sketch of how I think it could go together to make a system that could really work to supply hot water from an oven. What you see is a cross section of a cylindrical flu with a open top cylindrical water chamber around it. I've left out the controls it would take, but basically you would need a thermostat for the storage tank that would turn on the pump if the water in the tank needs to be heat. The pump then fills the water chamber on the flu until some type of control(like a float valve) tells it the chamber is full. The water is then heat until it triggers a thermostat in the water chamber that opens a drain valve and drains it back into the storage tank. Kinda complicated but it could be cobbled together from surplus controls and scrap pretty easily and would provide safe reliable hot water when the oven is running.
                    Attached Files


                    • #11
                      Re: Heating Water from FLU

                      Hi Jase,

                      Sounds like your've got some thinking to do, however thats half the fun with a new build... just make sure you post some work in progress photo's when you start & let us know what you've done different second time around.

                      Good luck Brett.


                      • #12
                        Re: Heating Water from FLU

                        Thanks for the input everyone. My Father in law has an instant hot water unit available so I might take the easy way out and use that for any hot water needs, and I dont like the idea of scalding hot water racing out the pipe and burning me or worse still my family.

                        My Bessa blocks are being delivered on Friday for the oven stand and I have all my other building materials ready and waiting to go. I hope to get the footings started this weekend, i will be taking lots of photos as i go.

                        Cant wait to get stuck in, dont reckon i will change much on the actual oven itself as i was real happy with my first one.