elevated water supply to pump

[blitz97]

Hey all - Working on my first water system design. In general, if the supply line to a pump is elevated, can this positive pressure be subtracted from the feet of head seen by the discharge? Thus reducing the size of the pump?

 

[LittleInch]

A centrifugal pump supplies differential head, therefore increased inlet pressure / head plus pump head equals increased outlet pressure/head for the same pump. The elevation of the pipe is not relevant, only the levation of the pump inlet compared to the elevation of the liquid level or pressure of the inlet to the pump. If the inlet head increases for a fixed outlet head, then the power of the pump would decrease, but volume and "size" could remain the same.

A PD pumps works quite differently, but increased inlet head can lead to increased outlet presusre, but not in the same controlled manner as a centrifugal pump.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[sspeare]

You say this is your first water system design. You should get the book "Cameron Hydraulic Data." The first chapter is an excellent treatment of pump inlet/outlet conditions, lift, suction lift, NPSHA, etc. The book is essential for anybody who designs piping and selects pumps. Good luck with your design!

 

[Artisi]

Agreed, "Cameron Hydraulic Data" will be one of the best investments you ever make if you are going to be involved in pumps / systems etc.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)