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Find out if the zone fits your water supply before you trench.
Every irrigation zone is a budget: your supply delivers so many GPM, and every head on the zone spends it. Overdraw and the last heads on the line barely spit. This calculator runs the two checks pros do — capacity (bucket-test supply × 80% vs zone demand) and precipitation rate against your soil's intake rate — so you know the zone works before the pipe goes in.
Irrigation techs use it to check a zone against the property's real supply before trenching — bucket test in, capacity verdict out. Homeowners adding heads to an existing zone use it to learn why the last head on the line barely spits: the zone was already overdrawn.
Because the bucket test is a best case. Static pressure sags when neighbors water, municipal pressure varies through the day, and valves and pipe lose capacity as they age. Designing to 100% of measured flow is how you get a zone that works in June and fails in August.
Spray heads put down roughly 1.5–2 inches per hour while rotors put down about 0.5. On one zone with one runtime, the spray areas get 3–4× the water of the rotor areas — drowned spots next to dry spots. Separate zones, separate runtimes, matched precipitation within each.
The water runs off instead of soaking in — wasted water and dry roots. Fix it with cycle-and-soak scheduling: split the runtime into two or three short cycles an hour apart, or switch to lower-precipitation nozzles like MP rotators.