On Sat, 20 Aug 2005 12:34:51 GMT, "Karl Townsend"
remove .NOT to reply wrote:

The bottom of my 30,000 gallon fish pond is full of sludge and fish s^&t. I
want to try to make a venturi style sump pump. These pumps are extremely
simple. They work by using a high pressure water jet to move a large volume
of water at low pressure.

Here's a little bitty one:
http://www.aquaticeco.com/index.cfm/...d/2556/cid/750

Here's one for a basement sump application:
http://www.pumpbiz.com/products/inde...&series_id=820

Here's one moving tens of thousands gpm:
http://tech.praqua.com/pdf/nb/2001/MayJune01.pdf

For my job, I have a 10 gpm 400 psi piston pump (tractor PTO driven hypro
model 5200). I have a 2" suction hose fifty feet long. I'm thinking of
building the pump into a 4" plastic sewer pipe Tee. The bottom of the Tee
would be the suction inlet. The right of the Tee would have the high
pressure water nozzle. The left of the Tee would be the outlet. It would
look just like the unit in the first link only a bit bigger.

I need design help. Specifically what size orifice should I try for the high
pressure outlet. And where should the orifice be located. Also 4" ID of the
tee is probably too large, what would be the best ID to use? Any other
suggestions?

The general idea here is conservation of momentum: high-velocity
lower-volume jet transfers momentum to lower-velocity higher-volume
flow, with said transfer of momentum resulting in lower pressure but
higher volumetric flow.

That's nice -- so how big? I'd start with seeing what size tapered
nozzle your pump can deliver 10 gal/min thru at 400 PSI. That's what
I'd use as a nozzle because it "matches" the pump.

Shoot that into a larger suction and discharge tube. What size?

The delivery flow and pressure difference (inlet to outlet) will
depend on the size of the suction and discharge tube, but you'll use
what you have at hand anyway so that's where I'd start. Try it, see
how it works. I'm guessing that it'll move quite a bit of water
with 4" pipe.

Let us know what happens!

It's pointless to get too worried about design because you'll use what
you have at hand anyway. Much quicker to just see what such a
nozzle does in a 4" suction and discharge line.