Posted: 08/04/2017 at 11:38
I wouldn't expect a gravity fed irrigation system to be able to feed many outlets, and it's difficult to see how many you are trying to feed on your system. Because the pressure will be greater the lower the outlet, those will be the ones which I would expect to get most water.
Water will flow through the system by gravity, but each outlet is designed to restrict how much passes through, and even tiny differences in manufacture will make a difference.
The system I use runs off an outside tap and there is a difference in flow on adjoining outlets. It's really a case of trial and error.