Does your system have “Mixed Precipitation Rates” in the same zone? Meaning, does the zone have “mixed head types” (Rotor Heads and Spray Heads)?
What does this mean?
A standard Rotor Head (3.0 gal/min. nozzle at 45 lbs. of pressure) will deliver 0.37 – 0.42 inches of precipitation per hour.
A standard Spray Nozzle (RainBird 10′ radius, 180 degree at 30 lbs. of pressure) will deliver 1.45 gal/min. totalling 2.80 – 3.23 inches of precipitation per hour.
What does this mean? The Spray Heads in the zone are delivering 6 – 8 times more water (precipitation rate) than the Rotor Heads. Since controllers run your sprinkler system per zone, that means that you are way over-watering the smaller areas of the zone (spray heads) while more correctly watering the larger areas (Rotor Heads). Or, if you change the controller to water less time to accommodate the Spray Heads, then you are way under-watering the larger areas (Rotor Heads).
Remove the standard spray nozzle from the Spray Heads and replace them with a Toro Precision™ Rotating Nozzle (the nozzles can easily be swapped without digging our or changing the Spray Head) to more closely match the precipitation rates of the Rotor and Spray Heads. A Toro Precision™ Spray Nozzle set at 180 degrees at 40 – 50 lbs. of pressure will deliver a precipitation rate of 0.56 – 0.64 inches per hour, which more closely resembles the rate of the Rotor Head. Therefore, the zone can be watered more evenly – even though there are two different types of heads on the zone.