1. #1
    Firehouse.com Guest

    Question Drafting from Porta-Tank

    You have (2)1000 gal. porta-tanks connected with a 3 inch pipe approx. 3 feet long and are drafting from just 1 tank. What is the maximum flow rate that you could expect to transfer from the second tank via gravity?

  2. #2
    Firehouse.com Guest


    184 gpm when full and 120 gpm when 1/4 full

  3. #3
    Firehouse.com Guest


    Thank you LHS.

  4. #4
    Firehouse.com Guest



    Run the math briefly if you have a minute. I wasn't sure that I quite had enough info.

    If the tank is 3 feet tall, would the following hold true?

    3 feet of height x .434 lbs per foot = 1.302 lbs of head pressure

    gpm = 29.7 x d squared x square of pressure

    gpm = 29.7 x 9 x 1.141 = 304.98 gpm

    Assume FL is neglible in 3' of pipe.

    Where did I go wrong Larry?

  5. #5
    Firehouse.com Guest


    Said duh about two minutes after hitting enter but could not figure out to delete my post. The two tanks are equalizing, doesnt matter how tall they are to begin with.

    So how do you figure the math. Is there a chart or a formula.


  6. #6
    Firehouse.com Guest


    I'd have to guess that the pipe is going up and over, not connected at the bottom. So the water has to go up, over and down negating some of the head pressure.

    Just a guess, we use the transfer hose already built into the bottom of the tank.

  7. #7
    Firehouse.com Guest


    Chris: You were correct the first time. Water flow will not occur without pressure. It can be from elevation (gravity/head) or atmosphere pressure (vacuum from siphon). The rate of flow is influenced by the pressure and the pipe's friction loss. The small diameter will limit the flow due to FL.
    I would expect little pressure which makes the FL a major consideration. Notice that Larry gave different flow rates which varied with the tank's content change.

    Hosekey21, why is it such a small diameter pipe?

    Larry, how did you figure the g.p.m. flow?

    [This message has been edited by DD (edited 12-02-2000).]

  8. #8
    Firehouse.com Guest


    Used hydraulics calculation software for transfer of milk from one tank to another tank. The big thing left out here that the software handles is back pressure during the transfer and its effect on flow. We use 10 inch drains to connect our tanks which exceeds the pump capacity of all of our rigs.

    Daisy chaining 4 to 11 4000 to 5000 gallon drop tanks is quite common out here. All connected with drains.

    Homemade jet siphons are used to transfer water when flows above 2000 gpm are needed. Each drop tank connects together with a 10 inch connector.

    [This message has been edited by LHS* (edited 01-13-2001).]

  9. #9
    Firehouse.com Guest


    Currently we do not have our tanks connected.
    The 3" size is choosen because that is the size of our current drains. I am looking into the possibility of connecting them somehow. I figure using this method could only yield about 250 gpm.

    We do not have a jet-assist transfer device. We have trained a little bit at using a suction hose over the top to transfer the water. This does not seem like an effient use of manpower to always have to prime this length of suction.

  10. #10
    Firehouse.com Guest


    Here is how my Old department did the Job.

    We went to the local hardware store and bought some brass piping and some regular straps. We the made them into a J shape. THe long end or the top of the J had a reducer on it sothat we could attach a 1 1/2 in line to it.

    We them took a single piece of hardsuction, or two pieces depending on the space B/T tanks. We strapped the short end of the J inside the drop tank and the long end running back along the length of the hard suction, where it connected to the 1 1/2 in hose. Put the J end in the full tank and make sure that is is fully submerged. Turn on your 1 1/2 line and the water will move from the full drop tank to the empty tank. Wallah. Water transfer. I think that was the ? you were asking.

    Take care

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