"~ jan" wrote in message
...
On Mon, 25 Jun 2007 09:31:35 CST, Kurt wrote:

Okay, RTB (or anyone), many moons ago there was discussion in old RP
regarding pumps needing a certain amount of head/back pressure to work at
their best. Is this still correct and is that also true of mag-drives?
~ jan
------------
Zone 7a, SE Washington State
Ponds: www.jjspond.us

I can remember the discussion, but I cannot find any info showing a need.
There were curves in old AES catalogs, I think, that showed electrical
consumption per gallon, or something like that, which are no longer shown.
The flow curve sweeps downward at an increasing rate with increased head and
the other curve swept upwards at an increasing rate with head. The most
effective use of the pump was the point where the two curves came together.
But, I have not found those curves today.