Velocity is the flow divided by the pipe cross-sectional area. For 350gpm, a ø 12" pipe is suitable.

fyi see e.g. Table 17-1 at site http://www.acipco.com/adip/products/Sect17.pdf, with I think 350 GPM equivalent to about 500,000 gal/24 hr (while there will be a headloss as a function of the pipe size and flow and in a sense it is dependent on your source as well, it appears you could be talking about eight or six inch pipe)

For a rough estimate, you can use this formula, well, it is a tip.

d in inch = 0.25 X Sq Root of GPM

then round it up to the next commercial pipe size and it will give you the proper sizing to start with. It works with water

example: 100 gpm will need a 2 1/2" pipe so use 3" line and it will give you Delta-P less than a PSI.

Regards;

Nadeem Butt

10222008

With the increasing cost of energy (electricity etc.) and if this happens to be a pumped main (and particularly if you must pay for the consumption of pumping energy!), you may want to look also at the "pumping cost" over the anticipated life of the pipeline. There can be VERY surprising difference in the present worth of pumping cost e.g. between an 8" main operated at less than 3 fps (<1 mps) flow velocitiy and say a 4" main operated at more than 8 fps (>2 mps), and the price of some larger pipes might now be easily justified (not to mention not having the incumbent environmental costs of the increased future energy consumption with smaller pipes).

[A computer program that can be downloaded for free (and manipulated with whatever assumptions you want to look at this) is incidentally available at the website http://www.dipra.org/ .]