Product review (5 stars): Works as advertised - amazing.
I had a problem with mine, it wouldn't produce the bubbles until I turned the faucet down.  Full open, no bubbles, 1/4 turn close and it works fine.  My water pressure is 60 psi and the unit requires 40 - 75 psi.  Not sure why turning it down helped, but it works, that's all that matters.  Hope this helps someone else.