Quick answer: There is no single correct run time for every sprinkler zone. Runtime depends on sprinkler type, nozzle precipitation rate, soil, slope, sun exposure, plant needs and weather. A rotor zone and a spray-head zone may need very different runtimes to apply a similar depth of water.
Why minutes alone can be misleading
Different nozzles apply water at different rates. Setting every zone to the same number of minutes can overwater one area while leaving another dry.
Watch the landscape and the water
Runoff, puddling and constantly soft soil suggest water is being applied faster or more often than the site can use. Dry patches may indicate inadequate runtime, but they can also result from poor coverage or a malfunctioning head.
Cycle-and-soak watering
On slopes or soils that accept water slowly, dividing irrigation into shorter cycles with soak time between them can reduce runoff.
Before increasing runtime to fix a dry area, make sure the system does not have a low-pressure problem or damaged sprinklers.
