"~ jan" wrote in message
...
On Sat, 23 Jun 2007 21:17:37 CST, Kurt
OP, I'm surprised no one asked or mentioned head, especially for a
MagDrive. The higher the head the quicker the flow rate drops on these.
Thus, check a flow chart: http://www.justliners.com/suprememagdrive.htm
For every 10' of pipe (and I'd recommend 1.5") count as 1' of head, so
according to this chart if you have 5' feet from surface to top of
waterfall and 10 feet of pipe you'll only get 950/gph.
------------
Zone 7a, SE Washington State
Ponds: www.jjspond.us

The head loss Jan mentions is a bit more complicated that 1" per 10" of
pipe. The chart shown at this link
http://www.aquaticeco.com/index.cfm/...Detail/ttid/54
shows that the head loss is a factor of flow rate in GPM and pipe diameter.
A 1200 gph pump would push 20 gpm with 0 head loss. As Jan says look at the
flow chart for the pump to see what flow you will actually get for different
head values for a pump. The chart shows that for 3/4 inch pipe at 20 gpm,
the head loss is 73 feet for each 100 feet of pvc pipe, for 1 inch the loss
drops to 23 ft. and at 1 1/2 inch the loss has dropped to 3 feet per 100
feet of pipe. Elbows, Tees and fittings all add to the head loss.