Hey Gui For me, the issue was the overall pressure of the system, meaning that if the pressure was high, the system worked better than if it was medium or light. I used to use salvaged latex whoopie cushions quite a bit for the pressurized air-bladder, and I found that if I doubled them up, one inside the other, that they were sufficiently robust to provide the higher air-pressure. An added benefit is that when one breaks, the instrument continues to function, but at a reduced volume... As for the air inlet/water inlet connection where the 3/4,3/4,1/2" cpvc tee meets the sprayer...It might give you a stronger mechanical connection if the stub coming off of the cpvc tee was 1/2" rather than 3/4" (like of you used a 3/4, 1/2, 1/2' cpvc tee). Here's why: often these sprayer things have a conical opening in the handle that the 1/2" pipe jam-fits into nicely... good luck!

Part 3 finally... my membrane pipes use a 3/4,3/4,1/2" cpvc tee or Copper tee which is with the 1/2" Cpvc pipe sticking right through and up to the top of the tee with either a latex glove/balloon or grocery bag membrane. The air inlet fits straight into the water inlet of the sprayers but requires glue or silicone to stay put. The only question i have left is how you got the sprayers to give enough air to the membrane pipes?

I screwed the CPVC Slip X MIPT fitting into it snugly, added some CPVC pipe, went to a CPVC 1/2" Tee, which was connected on the side to the Balloon, than on the bottom to more cpvc pipe, connected to a 1/2" Coupling which fit snugly into the 1/2" PVC Check Valve, followed by another 1/2 CPVC coupling, length of pipe, tube and High volume Air Pump.

Great! I got some 2" PVC and i was planning on sticking my sprayers (they were expensive) straight in with some clear silicone caulk or the hot glue also. I have the 2" Street Elbow, Coupling, and Reducer from 2" to 1/2". into the reducer, i screwed (Continued at Part 2)

Hey Gui! Let's see, The "main sewer-pipe" is some 1 1/4" pvc that I chose somewhat randomly to be my manifold body. I cut off some stubbs of blue 3/4" pipe that I forced into holes that I drilled in a line along a side of the 1 1/4" pvc. I had to hand-shape the holes in the 1 1/4" so the blue stubs fit snug, and I poured on hot glue after. I also bored-out the inside hole of the srubb-ends, so my sprayer-valves fit right. The check-valve is built into the foot-pump that I use. The under-structure has varied over time, and was most recently made from an old cymbal-stand. The whole organ got stolen from my truck recently, so I'm working on a newer, larger one from scratch.