Irrigation and Water Management
This domain tests hydraulics, zone design, scheduling efficiency and code-required protection: pressure, flow, precipitation rate, head layout, controller settings and backflow prevention.
Hydraulics
Static pressure is measured at rest; dynamic pressure is what remains while water flows and is what heads actually see. Keep velocity at or below 5 ft/s in lateral lines to limit friction loss and water hammer. A zone's flow is the sum of its head flows and must fit available flow at dynamic pressure, allowing for valve and meter losses.
Head layout and zoning
Space spray heads head-to-head, spacing approximately equal to throw, and use matched-precipitation nozzles within a zone. Never put sprays, rotors and drip on the same valve. Drip systems rate emitters in gallons per hour; use pressure-compensating emitters on long runs or elevation changes.
Scheduling
Replace the evapotranspiration deficit minus effective rainfall, and cycle-and-soak on clay soils: run, soak, repeat, so water infiltrates instead of running off. Zone by plant water need, sun exposure and soil. Water in the early morning.
Worked example
A zone of 12 spray heads at 1.5 gpm each = 18 gpm. If the zone covers 1,200 sq ft, precipitation rate = 96.25 x GPM / area = 96.25 x 18 / 1,200 = about 1.44 in/hr. Heavy clay may accept only 0.5 in/hr, so the zone must be split into several short cycles rather than one long run.
Traps
Sizing pipe and zones on static rather than dynamic pressure; mixing rotor, spray and drip heads on one valve; omitting the required backflow assembly and its annual testing; overspray onto pavement and siding; and leaving a controller on its spring setting all season.