Summary

I designed this to mix a small amount of liquid fertilizer into a stream of water from a garden hose.
I have a worm composter that produces quite a bit of liquid fertilizer and I wanted to dilute it and sprinkle it on my lawn.

Instructions

Print it out.
Break out the little support cylinder in the bottom and cut out the think membrane over the hole.

Place a rubber washer in the female threaded end.
Tap the vacuum port with a 1/8 NPT tap (don't force it and crack the plastic)
The hole is already tapered so hopefully it shouldn't be too much work to tap it.
Insert whatever 1/8" npt fitting you want into the port (JG fittings are nice)

Hook it up inline with your sprinkler or whatever.

4/16/16
I just ran the original venturi through netfabb to fix some problems. Hopefully it is good not.
Made a slightly different stl (called venturi 3.5) that should have slightly looser threads and has no built-in support material. I also ran this file through netfabb.

Garden hose venturi pump