In this video, This Old House landscape contractor Roger Cook shows how to increase the water flow for happier, healthy plants.
1. Attach a pressure gauge to the end of the garden hose that's supplying water to the irrigation system.
2. Remove one of the emitters (drip nozzles) from the irrigation tubing and attach the pressure gauge. The water pressure at the emitter should be about 20 psi (pounds per square inch).
3. To improve water pressure and flow, divide the irrigation system into two zones. Cut the tubing in the middle of the system, and seal off the cut-ends of tubing.
4. Retest the water pressure at the emitter. Again, it should be about 20 psi.
5. Now use two garden hoses, one to supply water to each half of the irrigation system.