The 5 steps:
The irrigation industry has accepted that certain design considerations must be met for a high-quality irrigation system. We spent years narrowing them down to the following five short steps:
Step 1: Determine your soil type to know whether to amend your soil. Amending soil is by far the single best thing you can do for your landscape. Just do it!
Step 2: Collect information about the plants to be irrigated to determine how much water it will take to support them on a regular basis. For example, are they all 1-gallon Southern California native shrubs that will grow 4 feet tall when mature? A mix?
Step 3: Collect information about the microclimates at the site to determine where you need to compensate for non-uniform watering requirements. For example, is a valve irrigating only in the sun, or does it wrap around a building into the shade?
Step 4: Calculate the number of gallons per day needed by the least-thirsty plant on each valve, to establish that valve’s base-line irrigation run time. For example, if the least-thirsty plant on a valve needs only .25 gallon per day, then two minutes per day (using one emitter) is that valve’s base-line.
Step 5: Calculate the number of gallons per day needed by the thirstiest plants on each valve, to establish how many more emitters to add for their higher water requirement. For example, if you add some plants to a valve that need twice as much water as the least-thirsty plants, which are using one emitter, then put two emitters near those thirsty plants.
See ReWater’s Owner’s Operation Manual for additional design criteria including the Hydraulic Operating Parameters Chart on pages 15-16 created by the Center for Irrigation Technology, as required by California law for emitters using untreated greywater.