Irrigation systems are both a curse and a blessing to our gardens. Most systems are designed for maximum area coverage yet are not very efficient in watering plants well. Landscape plants need different water schedules than grass does. Furthermore, most homeowners irrigate far too often and too lightly. Usually one heavy irrigation per week will suffice for most landscaping, twice a week on grass areas. A simple rain gauge placed in the spray area will let you know how much water is applied, with a target amount of 3/4" to 1" of water, once a week. This heavier and less frequent watering promotes deeper rooting and more drought tolerant plants.
We have a new comprehensive irrigation system at Pinecrest Gardens which is tailored to individual areas, and we water the gardens once a week. Some areas are irrigated with drip-line irrigation for maximum efficiency. Even the rainforest areas get watered just once a week, with 1" of rain and with excellent results. We've also used a lower analysis fertilizer to get plants to slow their growth and use less water.
Many people use a high-nitrogen grass fertilizer which leads to fast grass growth with shallow roots (leading to very thirsty grass, too). A more balanced fertilizer like 12-4-12 or 15-2-15 fertilizer along with weekly deep watering will give you better results and use less water than the common tactic of daily watering for 10 minutes. The plants will grow better, need less fertilizer, and we'll conserve our water resources. Regular maintenance on irrigation heads and attention to the controller schedule will keep the system trouble-free while staying in compliance with watering regulations.