Force Main Velocity (Vertical Piping)

[BluDev]

What are the recommended min. and max. velocities for the vertical section of pump discharge piping in a sewage lift station. I read >8.5 fps from one source. Any recommendations? Thanks for the help.

BluDev

 

[yogibear1]

Good question for the theorist;, practically speaking the vertical section of piping as well as the other sections should be designed for optimum economy both in intitial cost as well as life cycle operating cost. Crane Technical Paper 410 is quoted by many, such as The Piping Handbook, Sixth Ed., as the source for "reasonable" velocities - no mention of direction. In Crane, General Service Conditions is up to 10 fps. Sewage should not settle in vertical or horizontal runs at a velocity of 8.5 fps, which also favorably compares to what I heard in a pump seminar that a happy pump has an output vlocity of 5 to 8 fps.

 

[bimr]

You do not have to use any different pipe size on the vertical pipe segment in the lift station than the rest of the piping system.

If you have any significant pipe length (over 200-300 linear feet), then the typical design pipe velocity that is used in municipal systems is 3-5 ft/sec. If you use higher velocities, then you are going to have to install excessive pump HP to pump the fluid.

If you buy inexpensive lift station packages from low bid suppliers, you are probably going to find the pipe sizes to be at the margins.

Not familiar with "happy" pumps myself.

 

[yogibear1]

Yes, I know "happy" pumps sounds kinda corny, just a euphemism, like operating at the "sweet spot" on the pump curve.