venturi water pump design

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/fuseaction/product.detail/iid/2556/cid/750
Here's one for a basement sump application: http://www.pumpbiz.com/products/index.cfm?fuseaction=pump_series&series_id 0
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?
Karl
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If you are located near a gold mining or an old gold mining area go to a shop that sells sucker dredges. They might even rent you a venturi. Also google KEENE [sp] they are a big mfg of such. The older ones I used were not very sophisticated. I built a 4" one fed by 1 1/2" hose necked down to 3/4" aimed into the 4" at about20 to 30 deg. Hope this helps.
Chuck P.
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If anyone knows of a source for this (cheap) I'd like to just buy one. I'm in Dassel Minnesota - no gold but there is iron mines on "da range" (Northern MN) Karl

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I'm no expert on these but most of the water well jet pumps have a fairly high percentage of inlet water to outlet water. Someting on the order of 1/2 the output is pumped down the well. The other thing is that the the pressure is not that high. So you need high volume, medium pressure.
For your 10 gpm pump I consider using one of those garden hose "sweep" nozzels. I have an all brass one, one piece, approximately 3/8" inside diameter necking down to a bit over 3/16" (or build your own) Your pump is higher pressure, I'd shink the outlet to around 1/8" to max out the capability of pump. You want max pressure and max volume. Make a couple, cut the end off until the performance drops, cut a fresh one to the optimum length.
With only 10 gm, I'd guess that you don't want much over 1-1/2" pipe as your outlet in the orifice area. Smaller diameter will give you higher outlet pressure. How much head do you need? It works better if the pressure blast goes directly down the center of the output tube. A somewhat longer outlet tube (perhaps 10x the diameter) should help couple your high pressure blast to the inlet water.
Cheers.
Karl Townsend wrote:

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I also have a 15 hp. irrigation pump I could use as the pressure supply. It puts out 140 gpm at 125 psi . I thought this was overkill, but I don't care. I need to create maximum suction and have large opennings. The stuff at the bottom of the pond is liquid but very heavy - moose muck. I sucked a rock into my centrifical trash pump and stalled it. (Kids LOVE to throw rocks in water - skip-skip-skip) Would this work better??
Karl

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I am also no expert, but I would expect that the horse power needed to drive the pump would be the key. Fewer gallons per minute at higher pressure would work as well as higher flow at lower pressure.
Before I built a venturi water pump I would think about draining the pond and using a front end loader. Could you start at one place and clean out to firm footing so you don't get stuck? Do you have a backup plan if you do get stuck?
If you do build a venturi pump, I would scale up from a jet water pump for the design. Probably use a smaller orfice since you are not using a centifical pump and boot straping the output . I would also consider another jet in front of the inlet directed to stir up the muck. If you put a screen in front of the inlet, you could use your trash pump to help suck the stuff through.
Dan
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" snipped-for-privacy@krl.org" wrote:

I'd think "hydro-dredging" would be a lot easier than draining and using heavy equipment, but I thing you're over engineering it with the venturi pump idea.
Make an intake nozzle assembly to fit the suction line of your trash pump out of sheet metal that flares out and tapers down to a long rectangular inlet with the narrow section the same width as the solids rating of the trash pump. Weld pieces of 1/8" rod across the opening at the same spacing to provide support and act as an inlet screen.
Mount a suitable piece of pipe perhaps 6" back from and parallel to the suction opening. Drill a series of holes along this pipe to act as nozzles to shoot water back at the suction inlet. Use appropriate fittings to provide inlet water to the jet pipe from a source inline with the suction hose.
Cable tie your hoses together and then use your high pressure pump to provide the jet water to loosen the sludge and push it towards the suction and the trash pump to suck the muck up to your settling pond. Drag the sweeper around the bottom with the hoses as needed to clear the muck.
Ok, so that idea is over engineered as well, but I think it will work better.
Pete C.
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Moose muck requires moose horsepower. I like the idea of using a trash pump, proper guards to keep the big crud out, and some sort of power wash from your high pressure pump to keep things moving.
snipped-for-privacy@krl.org wrote:

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Based on today's discussion, I'm going to buy a 2" Y, hook the 2" suction hose up to the slant side. Put a 1/2 pipe for a nozzle inside the acute side of the Y and hook this up to the irrigation pump<125psi 140 gpm>. I'll put a 2 foot length of 2" pipe on the obtuse side of the Y for the reduced section. And then vent to air. Fire up 15 hp irrigation pump and jump in pond, move hose around bottom while its full. I'll make it so I can move location of nozzle and may try difffernt lengths of obtuse side pipe. This whole thing won't take more than an hour to build.
If it don't work at least I'll have one more trial. I've give up on the trash pump I have - not enough ability here. A serious trash pump looks to cost north of $1000.
Karl
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Why reinvent the wheel? You can buy a perfectly good submersible sewage pump for about $40 at any good hardware store. It won't constantly plug up like a venturi does. . . . constantly. All you add is hose and power. Bugs
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Put some steel screen over the opening of the hose and you won't gather the stones into the pump! You should always run a pump with an input screen or you will get sheared shafts and all kinds of other nice things in the pump! While you are at it, take and put a minishovel on the end of the hose also to muck about in the harder spots.
-- Why do penguins walk so far to get to their nesting grounds?
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On Sat, 20 Aug 2005 12:34:51 GMT, "Karl Townsend"

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Hey Karl,
No expert here, but I think I'd try a 22 degree "T" first to get an assist angle for the suction. High pressure applied straight thru, with suction on the "angle".
Again no expert, but I would think a much higher volume pump would be required than the 10GPM. This style stuff works but works best when there is an over-abundance of cheap or free power system available, or used when there is a need for low head-space/clearance or where no electricity is allowed for sumps. I used to see them a lot in old elevator pits with maybe only a 2" deep sump spot, before they were outlawed by the newer plumbing codes. City water pressure to operate them is cheaper than you can buy electicity. They don't lift "dirt and debris" any better than a centifugal pump though, and will never approach a guzzler type for moving trash.
Take care.
Brian Lawson, Bothwell, Ontario.
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Karl Townsend wrote:

Why not use the waterpump just to loosen the 'mud' and then use an air-lift system to suck it up the discharge pipe? 5 to 10 pounds of air (a few CFM) injected into the discharge near the inlet will move a lot of liquid.
Ken.
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On Sat, 20 Aug 2005 12:34:51 GMT, "Karl Townsend"

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.
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LOL You must know me pretty good. This is just what I'll do on trial one.
Still, the engineer in me likes to understand the concepts and best design. If the idea has merit, I'll want to make a second and third run. In the case of pond cleaning, I want to make it so its quick and easy to do.
P.S. I WILL HOB GEARS THIS WINTER
Karl
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On Sun, 21 Aug 2005 12:13:55 GMT, "Karl Townsend"

Good! I want to make an electric drive for my boatlift, may need a gear or two! Electric boatlift drives are available, but the prices they want are outta sight -- nearly $600 list. That's nuts! I'll spend quite a bit of enjoyable shop time this winter rather than pop six bills for such a gadget. Porta-Dock right there in Dassel offers them, though I don't know if they make them there. There are several small companies in MN that make them.
Doing some quick calculations based on conservation of energy, I figure your 400 PSI 10 gpm jet would move about 266 gal/min thru a differential pressure of 15 PSI. That doesn't take losses due to turbulence into account, and these losses could be considerable. The trick is to get the suction pipe diameter so that the energy from the jet couples well to the discharge flow. I haven't a clue how to calculate that, but some quick experiments should be enlightening.
I wonder if a tapered housing or venturi might work well, to minimize circulation and turbulence where the jet meets the flow. The high-velocity jet entrains a high velocity flow in the venturi region which then expands to become a lower-velocity higher-pressure flow to the discharge.
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... They are indeed made right here in Dassel. I know most of the folks that work there. But, you can copy one for a tiny fraction of the retail price.

I'll be machining a venturi insert to fit inside a large pipe for this. ( quick and dirty - drill hole and taper in piece that I can weld inside a pipe) I took a jet pump jet apart and I'm just going to scale up and copy the design. As I'm not concerned about flow rate but maximum suction is a priority, I'm going to guess that the venturi should be relatively smaller (give higher velocity to the water). As I need to allow for a 1" stone going through, I'll keep the jet nozzel back a bit from the small part of the venturi. I'm making it so the nozzle can be moved so I can play with location. I'll start with a 3/16 diameter nozzle - I know the pump settles at 175 PSI with 1/4" - just a wild guess that 3/16 will be about right.
Something like this is fun, thinking on this beats the heck out of (watching) the drivle on TV.
Karl
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On Mon, 22 Aug 2005 02:13:59 GMT, "Karl Townsend"

Sounds good to me!

Oh yeah! Hey, maybe Grissom should make a venturi out of duct tape to suck out a cesspool for forensic evidence on CSI! "Greg, we're looking for DNA; I think the perp spit in the sink. We have a 200-gallon sample for you....."
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