Choosing the most suitable sprinkler heads for your landscape takes careful planning. There are so many sizes, shapes, models, and brands to consider that it can be difficult to make a decision if you’re not familiar with the basic types.
Generally, sprinkler heads can be divided into two broad categories based on the method used to spread water: rotor types, and spray types.
Rotor-Type Sprinkler Heads
Most people are familiar with the “impact” rotor that rotates in a jerky manner, making a distinctive noise as it shoots out bursts of water. Impact rotors (also known as impulse sprinklers) rotate streams of water back and forth, or in circles, usually in arcs ranging from 40 to 360 degrees. Most have a spray radius of 20 to 150 feet, with a precipitation rate of 0.1 to 1.5 inches per hour.
Little change has been made in their simple design over the decades — a spring-loaded swinging arm that breaks up the stream of water flowing from the head as the sprinkler turns. There are no small gears or seals to get clogged by dirt or debris, which makes them ideal for dirty or hard water (e.g. well water) applications. Made of high-quality metal, or heavy-duty plastic, they’re designed to work with high water pressure. They can be mounted on a riser, tripod, wheeled base, metal ring base, or inserted into the ground by an attached spike.
Pop-up impact sprinklers (they pop up from the ground to water, and retract when finished) are an available option for irrigating large residential or light commercial properties. Their straight-through flow design also makes them an excellent choice for reclaimed or well water applications. Pop-up impacts have a spray radius of up to 80 feet.
Although impact sprinklers have been replaced by gear-driven rotors in many situations, a variety still remain in use. Brass/bronze impacts (impulse sprinklers) are ideal for rugged terrain, and they’re also suitable for farmlands, large commercial and residential properties, parks, golf courses, and large gardens.
Turf rotors are the sprinkler of choice for a large, modern irrigation system. You’ll find them on golf courses, and in big, public parks. They’re large, pop-up gear-driven rotors that have a spray radius of 50 to over 100 feet, with full circle and adjustable arcs of 30 to 345 degrees. Their precipitation rate ranges from 0.57 to 0.69 inches per hour, and they also run with high water pressures.
A sprinkler of this size usually operates by having its own solenoid valve connected to a control wire and common ground that goes back to the controller. This is known as electric valve-in-head (EVIH) actuation. Some turf rotors are operated hydraulically, with a small control tube filled with water acting as the signal wires that connect to an electric contoller equipped with a hydraulic converter.
Gear-driven pop-up rotors are popular for medium- to large-scale areas, such as athletic fields, commercial sites, and residential areas, because of their quiet operation, low maintenance, and choice of spray patterns. These rotors use nozzles, and most manufacturers provide a nozzle tree with at least a dozen nozzles for each of their rotors. The nozzle selection makes it easier to achieve the desired radius and precipitation rate for each irrigation zone. The enclosed body of the rotor prevents dirt and debris from clogging the drive mechanism.
Usually, the spray radius spans from 18 to more than 70 feet, with an arc rotation of 40 to 360 degrees. Precipitation rates range from 0.2 to 1 inch per hour, depending on the pressure (25 to 75 pounds per square inch), nozzle size, and zone layout. They’re available in pop-up heights from 2 to 12 inches.
Because they apply water at a slower rate, medium-sized gear-driven rotors are a better choice than spray pop-ups for dense, clay-like soil, or sloped areas. The lower precipitation rate increases water absorption, preventing runoff and conserving water.
Rotary nozzles, or rotator nozzles, are very small rotors that are the same size as the standard nozzles on spray-type sprinklers. They actually fit onto the smaller, less expensive, pop-up spray sprinkler bodies, and thus are classified as “spray heads” in most manufacturers’ catalogs. You can identify them by the multiple streams of water that look like spider legs rotating around the nozzle.
These small rotors have a lower precipitation rate, 0.4 to 0.6 inches per hour, which improves water absorption and reduces runoff. They’re considered more efficient than spray sprinklers because they produce less mist, allowing more water to reach the ground. Rotary nozzles are suitable for narrow strips of grass, irregularly-shaped landscapes, and for smaller and intermediate-sized areas.
Generally, they have a radius of 15 to 35 feet, with arc rotations from 45 to 360 degrees. The radius and arc rotation are adjustable.
Older irrigation systems can also be retrofitted with rotary nozzles, lowering and equalizing the pressure among all zones, while at the same time getting more coverage.
Matched Precipitation Rate
In Texas, matched precipitation rate (all sprinklers in a zone irrigating at the same precipitation rate) is mandated by the Texas Commission on Environmental Quality (TCEQ). Matched precipitation rate (MPR) nozzles produce a uniform amount of water across each square foot of irrigated area, regardless of their spray arc. You must select the appropriate nozzle for each rotor sprinkler in the same irrigation zone to match the precipitation rate. This is why different-sized nozzles are provided with each rotor.
Spray-Type Sprinkler Heads
Spray sprinklers, or fixed spray heads, are stationary nozzles that spray a fan-shaped water pattern. They’re attached to stems that pop up from the ground to irrigate, then retract when not in use. Interchangeable nozzles are used to change patterns (1/4 circle, 1/2 circle, etc.), and the distance of the water throw. Spray heads work best for smaller areas, long narrow strips, and sections with tight, curving edges.
Pop-up spray heads have a spray radius between 3 and 15 feet, and their precipitation rate varies between 1 and 2.5 inches per hour. To work properly they need between 20 and 30 psi (pounds per square inch) of water pressure. Their pop-up heights are available from 2 to 12 inches.
Unlike the situation with rotor nozzles, spray nozzles come in matched precipitation rate nozzle sets, which means you can mix and match nozzle patterns on the same sprinkler zone, and the precipitation rates will still match for all the heads. Make sure you’re buying the nozzles marked “matched precipitation”, and that the nozzles are made by the same manufacturer.
Sprays, rotors, and rotary nozzles have models that can be mounted above ground on a vertical pipe to water over the top of tall, dense shrubs. These are referred to as shrub-type sprinklers.
- Rotor sprinklers
- Spray sprinklers
- Check Valves
Low head drainage occurs when water flows from sprinklers at the lowest elevation after the system shuts off. It can even happen with an elevation change of less than one foot.
Installing check valves in existing sprinkler heads, or replacing them with sprinklers that have built-in check valves, will prevent the leakage. Sprinkler check valves work by closing and holding water in the pipes when the system is off.
- Pressure Regulating Heads
Installing sprinkler heads in the same zone with built-in pressure regulators compensates for excessive or widely fluctuating water pressure in the irrigation system. By maintaining a contant pressure, the pressure regulators allow the nozzles to distribute water evenly. This reduces water waste, saves money, and extends the life of your sprinklers. In fact, the TCEQ mandates methods to achieve its water pressure requirements to “include, but are not limited to, flow control valves, a pressure regulator, or pressure compensating spray heads”.