Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Hot Water Tank: Reverse Return

Hilly
Hilly Member Posts: 418
When doing reverse return with water heaters are there considerations to take into account? I know when you do cascading parallel piping everything has to be perfectly equal. I am going to look at a project that may want the option for a 3rd tank down the road and reverse return seems like the most logical solution for tidiness and future expansion purposes.


Comments

  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    Size pipes based on connected flow. In other words, if the cold supply is 1" and tappings are 3/4", then cold starts out 1" until first 3/4" drop, then 3/4" to second tank. Pressure drop through both tanks must be the same, or as close to same as possible.

    Hot starts out 3/4" then jumps to 1" once it picks up the second tank. If piped as shown in your drawing due to piping being held so low, if one tank fails, you will have to shut off all tanks in order to replace the bad one.

    Hold all piping, isolation valves etc higher than the tops of the tanks, with unions on the drops high enough to allow isolation and removal without to interrupt the operation of the non affected tank. It's not going to cost a whole lot more money, but will make future service and replacement for whomever has the task.

    If pressure drops through all tanks (you can parallel as any tanks as you want) are the same, on draw, all tanks will see the same flow through their respective tanks.

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,839
    edited November 2017
    Some examples. Piping was not held high in drawing for drawing clarity's sake.



    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
    Henry
  • hot_rod
    hot_rod Member Posts: 18,177
    a few options, the low lead QuickSetter can balance multiple tanks and save piping. It also shows flow rates. These are indirect tanks with piping options on both coil and tank.

    Ideally with RR you should step the piping for perfect balance.

    Good info in Idronics 17
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Hilly
    Hilly Member Posts: 418
    Thanks guys. I'll get some more info today about the project.