Piping Layout/Calculation

[bicolexpress]

I am presently designing a water supply system that would
supply a 12 individual tanks at the same rate (GPM/Tank)
in contineous operation. I have Pump with 3HP motor, 115GPM,and with 1-1/2" discharge pipe coupled to a dia. 4" x 82' lenght pipe where 24 pcs of 3/4" x 2.5'lenght are connected to supply 12 Tanks (at 2 pcs each). How can I
ensure an equal supply rate(GPM) on each Tank? The Pump
location is at one end so I'm wondering if I can have an
equal supply rate in all tanks...

 

[TD2K]

The pressure drop through your system is pretty low, what sort of discharge pressure does the pump put out?

I would want to take the majority of the pressure drop across the individual legs to each tank, that will tend to distribute the flow to each tank fairly equally. Right now, you are taking more pressure drop over the 82' of 4" header than over the 3/4" legs to each tank and that's not going to give you similar flows.

 

[bicolexpress]

The theoritical pump discharge pressure is at 20psi.
Individual legs are placed at the top of the header
to supply the tank over it. For a 4" x 42' pipe,
the pressure drop is only at 0.3psi. If i have to compute
for the pressure drop on individual legs, it would be
different on each leg and therefore flowrates would also be
diff. Is there any other method other than changing
diameters on each legs or providing flow control valve on
each legs since those will affect our budget for the said
project.... Thanks.

 

[TD2K]

Since you have lots of pressure, I would put a smaller valve in each leg. Let's say you run 10 psi on the upstream side of the leg in the common header. Any minor differencs in piping lengths would be dwarfed by the resistance of this valve.

Take a look at the dP across a 1/2" and maybe 3/8" ball valve for the flow down each leg. Basically, you make them an orifice. I can give you a rough idea of the dP if you give me an ID for each of those sizes.

 

[bicolexpress]

Header's I.D. is 4.026" and Legs' I.D. is 0.742".