Irrigation Design, Installation, and Water Management
Design fundamentals
Begin with the water source: meter size, static pressure, dynamic (working) pressure, and available flow in gallons per minute. Design zones as hydrozones with similar plant type, sun exposure, and root depth. Space spray heads head-to-head for uniform coverage, use matched precipitation nozzles within a zone, and separate drip from spray on different valves. Provide backflow protection on any connection to a potable supply, install a filter and pressure regulator on drip, and use check valves on slopes. Add a rain sensor or smart controller and set a seasonal schedule from evapotranspiration data rather than a fixed clock.
Water management
Deep, infrequent cycles encourage deep roots. Audit the system: catch-can tests reveal distribution uniformity and precipitation rate, and a zone running at half its designed rate usually indicates a leak, clogged nozzle, or pressure problem.
Worked example
Twelve spray heads flow 1.5 gpm each over a 1,200 square foot zone. Total flow = 18 gpm. Precipitation rate = (96.25 x 18) / 1,200 = 1.44 inches per hour. If the plants need 1 inch per week, run time is about 1.0 / 1.44 hours, roughly 42 minutes per week split across two or three cycles.
Traps: confusing static with dynamic pressure, mixing drip and spray on one valve, and sizing pipe to velocity limits rather than pressure loss.
Rule of thumb: keep velocity under about 5 feet per second in laterals; the 96.25 constant converts gpm and square feet to inches per hour.