How many sprinkler heads should be put in one zone?

A zone is a group of sprinklers connected together by a system of lateral lines and controlled by a single control valve. A zone is determined primarily by available pressure and maximum flow and further determined by solar exposures, topography, plants’ water requirements and precipitation rates.

Sprinklers should first be zoned according to the available pressure and maximum flow. The maximum flow rate of a typical residential water service is around 11 gpm to minimize pressure loss. If you had a turf zone with 22 1-gpm spray heads, it would have to be separated into two zones of 11 spray heads each, so that the flow rate of each zone doesn’t exceed the available 11 gpm. 

Sprinklers should also be zoned according to different solar exposures such as shade versus sun, i.e., hot south and west exposures versus cooler north and east exposures, etc. Sprinklers at different elevations should also be on separate zones to better control the application of water and runoff. For example, the top, middle and toe of slopes should all be on separate zones. Separate zones should be established for plants with different water requirements such as lawn versus shrubs.

Different precipitation rates require different watering times, so they also need separate zones. For example, full-circle rotors may have to be separate from half-circle rotors. Also, rotors should be separate from spray heads, and spray heads should be separate from bubblers and drip. Combine any of these together and you’ll have to overwater some areas to avoid dry spots in others. However, with matched-precipitation-rate sprinklers, you can mix and match different nozzles and radii within the same family while maintaining even coverage.