I tried using a Venturi on my strawberry towers. I built a small PVC manifold, but used straight tubing. From the information I received, the bends in the tubing break up/slow the water flow (doesn't seem reasonable if I'm still pumping in the same volume) or some such story which impairs the uptake of the fertilizer.

I also found that the only Venturi's which really worked were from Mazzei; all of the eBay knockoff/competitor's versions either didn't work, didn't work consistently or had other issues (like threading).

Good luck.

while I have no experiance with venturi injectors, I can conferm that the more turns you have in your flow the more pressure loss you will have from turbulance and friction loss.