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Advice- 2 tanks w/ return

bdjjmj Member Posts: 2
I am trying to add an additional 275 tank to a set up. I have a miller furnace in a mobile home currently connected to a single 275 flat tank in an outdoor insulated building. The current hookup has a supply & return line dropped into a top bung with no filter. I have purchased and placed a second flat tank level & next to the existing tank. My question is what is the correct way to pipe these tanks together? Particularly in regard to the supply & return?

Do I drop a supply & return into the 2nd tank and then tee the two returns & two supply together? Or pipe the two tanks with a cross over & keep the single supply/return?

If lines for both how far should the lines drop in the tank would the 2' from bottom 1" from top rule apply to both?

I assume two fills/ two vents is the safest bet either way?

Thanks for any advice. Done many 2 tank setups, but not with flat tanks & a two line system.


  • icesailor
    icesailor Member Posts: 7,265

    I hesitate to suggest anything because what you are trying to do from a physics point of view, it is easy but very difficult.

    If you use a Tigerloop, use only one of the two lines for the suction on both tanks, and no return back to the tanks (because you don't need a return, regardless of the unequal level of product in the two tanks, they will equalize and draw down together. It will always suck off the highest filled tank until they are at an equal level. Put another way, have you ever seen the water level in a Lake that was higher at one end than the other?

    That's how two Roth's work. What you are doing may have Code issues. I'm not addressing that. That's your issue.
  • bdjjmj
    bdjjmj Member Posts: 2
    Thanks & another thought

    Thank you for your responses, it is helping me to wrap my head around it.

    IceSalior- In considering your hesitation from a physics standpoint. Would it be wiser to leave the return in the top of tank 1 and pipe together both tanks at the bottom into a single bottom feed supply line (again with 2 fills/2 vents)? The supply from the bottom would also keep the two tanks with equalized oil would it not?
  • icesailor
    icesailor Member Posts: 7,265

    If you use a Tigerloop, you don't need a "return". The Tigerloop is the return. If the supply(s) go into the top of the tank from the Tigerloop inlet, both tanks will draw equally. One can't draw more than the other because connected liquids seek their own levels. Two Roth type tanks draw off the top and both will always be at the same level.