GL's simple home made vacuum Venturis

Revised 13 March 2007:- Added copper-tube venturi at end of page.

This is the same venturi shown in the venturi test rig video on the eco-system website here.

It is a simple, low-cost, easy to make vacuum venturi, which can be used for many applications where you may want to create suction.

Here's a video of the venturi in action. Sorry it's sideways and poor quality!

Because it is made from standard plumbing parts, you can add it easily to your system. It is mainly intended to be used in various biodiesel manufacturing applications. ( Example... )

It is not particularly sophisticated, so won't offer high efficiency and can't pull a really low vacuum, but it is ideal for such applications as ...

  • Methoxide dosing. No need to gravity feed, this venturi will suck methoxide up and mix it into the flow of oil.

  • GL's fume-free reactor and distillation process. The venturi provides the suction to keep vapour flowing through the condenser in a closed loop, sealed system.

  • Siphon-starting of liquids you'd really rather not get near your mouth.

Here's what you'll need...

1. A brass Tee compression fitting, to suit your pipe diameter. I've used a tee with 22mm ends, and a 15mm side. You could use 1" or 3/4" Tees.

2. Two short lengths of pipe with perfectly flat-cut ends. I use a wheel-blade pipe cutter (the blue thing, top-right) to ensure the ends are perfectly true.

3. A sheet of flat cardboard. Cornflake packets are ideal.

4. A pencil and a pair of sharp scissors.

5. A large reel of un-fluxed plumbing solder.

6. A SMALL amount of plumber's flux. Use only when directed.

7. Wide-jaw vise or WorkMate.

8. Propane or Butane gas torch.

9. A 12mm diameter drill bit.

10. A 4mm diameter drill bit.

OK, let's make it...

Accurately draw around one of the pipes, to make 6 circles on the cardboard.

Cut out the circles as accurately as possible, and place 3 in each end of the Tee.

The cardboard circles will act as gaskets, to seal molten solder within the central chamber. I've used 3 to have enough compliance to ensure a good seal is made.

Here's a cutaway view of what we want to achieve...

Now place the two tubes into each end of the tee, and press them against the card to seal the central chamber.

Here's the assembly squeezed tight in a vise, to ensure the gaskets are well seated. I screwed on the compression nuts to help improve alignment, but I didn't used the compression olives - no need to waste them for this part of the process.

Here's what we're aiming for ...

Heat up the Tee with a blowtorch and fill the chamber up to the level shown - no higher, or you'll have trouble fitting the side tube. Whilst still molten dab a VERY small amount of plumber's flux around the top of the solder pool, to ensure it wets to the brass fitting. DON'T add flux before you add the solder, or it will sputter and bubble.

Let the solder cool down, then remove the assembly from the vise, remove the two tubes and the cardboard gaskets and see how well the cast has poured. There should be no air bubbles or gaps, and the solder faces should be flat.

This is what you should have now...

Now, using a drill stand, drill thru with a 12mm bit as shown, and then use a 7mm bit to make the suction port. Angle the bit as you see here, the ain is to get the suction port just breaking into the downstream bevel.

Now bevel the edges of the fluid-flow faces using a suitable larger drill...

Pump water thru it and place a finger over the suction port. You should feel a definite firm suction.

Well done! You've made your own venturi vacuum generator.

Coming soon - Transform the performance of this fairly crude venturi with a smooth tapered inlet and outlet. Specially made by Mike of JTP Inc. in Shillington PA 19607 Tel (610) 777-4890 ...

( See an example ) of a system which uses the venturi for de-watering, injecting and mixing methoxide, and methanol/water removal.

Latest Experiments...

12 March 2007:-

Why didn't I think of this before? Copper is so malleable, tonight I got the idea to try beating a copper tube into a venturi shape.

Wow! It is so easy!

And therapeutic .... bashing away at lump of copper this evening has made me feel at peace with the world, well, not quite, but for a first-timer I recon it came out OK.

With a little practice, it should be possible to craft your own high performance venturi within an evening.

Here's what I used ... a lump hammer as an anvil and a 38mm socket as the hammer. To get this far took 20 minutes of bashing...

My daughter took a video of the work in progress so you can see the simple technique I used.

Just keep rotating the tube and use just enough clout to slightly dent the tube each time. Angle the tube against the face of the hammer to create the longer output flare.

I did this 1st trial with an old piece of 15mm tube.

My next effort will be to create a working version from 22mm dia tube. Then I plan to drill a few small holes radially around the constriction and slide it into a 22mm:15mm:22mm Tee.

Interestingly, this venturi is easy to blow down in one direction, harder to blow down in the other...

13 March 2007:-

OK, here's the 2nd attempt at beating a venturi from copper pipe. This time a 22mm diameter venturi with 8mm diameter throat, approx.

This took around 3 hours to make. It has a 5mm suction port on the side.

Venturi inlet port

This shape works well. I could lift 8 feet of water using the garden hosepipe as a feed. Not tried on the reactor yet.

home made venturi from beaten copper pipe

Here's another one I made to the same design, fitted onto my processor. This is still in use.

venturi fitted onto my processor

Some other videos showing the venturi effect ...

This demonstrates the pressure profile along the length of a venturi...

Other home-made Venturi and Eductor designs...

1. From Ant on the forum...

Read about it at

2. From Twenty4seven on the forum...

Read about it at

3. From dickjotec on the forum...

Read about it at

4. From JohnO in Moses Lake, USA...

Read about it at

Graham Laming

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