Several companies make lawn sprinklers, which come in three main styles. Spray-type sprinklers deliver an even stream of water, while rotary sprinklers rotate as they spray a single stream. Impact sprinklers, which can cover wide areas, operate like rotary sprinklers, but they don't pop up. You can adjust all three types of sprinklers with a flat-head screwdriver and pliers, and in most cases, you can do it whether the water is on or off.
Adjusting Spray-Type Sprinklers
Not all spray-type sprinklers are adjustable -- some are preset for specific patterns, and the pattern width is usually displayed on the spray head in degrees. If the arc is adjustable, you'll see a single slotted screw in the center of the head. Set the left edge of the arc by turning the sprinkler sleeve, then hold the sleeve and turn the screw -- counterclockwise to reduce the width of the arc and clockwise to widen it. The maximum pattern width is often 360 degrees. It's easiest to do this when the sprinkler is on and the head is already above ground. If the water is off, pry the sprinkler out of the ground with the screwdriver and hold it while you turn the screw.
Rotary Sprinkler Radius Adjustment
Rotary sprinklers have two adjustment screws: one for arc width and one for spray radius. You may have to consult the information sheet that came with your sprinkler to determine which screw is which. You can also usually find the information on the manufacturer's website. The spray radius adjustment is the easier of the two to adjust: Turn the adjustment screw clockwise with a flat-head screwdriver to reduce the radius -- this drives the screw into the spray and disrupts the water flow. Turning the screw counterclockwise has the opposite effect. If you're making a first-time adjustment, back the screw out until the spray is at its maximum, then turn it slowly clockwise until it's at the proper setting.
Rotary Sprinkler Arc Adjustment
Before you make the arc adjustment on a rotary sprinkler, you have to set the stop point; on most sprinklers, this is on the left side of the arc, but on some, it's on the right. Holding the sprinkler sleeve steady with one hand, rotate the head all the way to one side then all the way to the side specified by the manufacturer as the stop point. Turn the sprinkler sleeve to align the stop point with the point on the lawn you want the water pattern to begin. The next step is easiest with the water on. Turn the arc adjustment screw clockwise to widen the arc and counterclockwise to narrow it. Let the sprinkler go through a cycle, then fine tune.
Adjusting an Impact Sprinkler
Impact sprinklers don't have a radius adjustment, and you adjust the arc with stop clamps. The clamps are designed so you can squeeze them with your fingers, but you may need pliers to do it. Turn the sprinkler head to the left until it lines up with the left side of the garden or lawn, then squeeze one of the clamps and rotate it until it's against the tab extending down from the sprinkler head. Move the head to the right side of the spray area and adjust the other clamp in the same way. Finish up by turning on the water and fine tuning.
When adjusting sprinklers while the water is on, the best strategy is to stay out of the water flow. You're bound to get a little wet, though, so wear appropriate clothing. You should adjust the sprinklers so all parts of your lawn or garden get water. If a sprinkler doesn't reach far enough, consider replacing it with one that will.
Chris Deziel is a contractor, builder and general fix-it pro who has been active in the construction trades for 40 years. He has degrees in science and humanities and years of teaching experience. An avid craftsman and musician, Deziel began writing on home improvement topics in 2010. He worked as an expert consultant with eHow Now and Pro Referral -- a Home Depot site. A DIYer by nature, Deziel regularly shares tips and tricks for a better home and garden at Hunker.com.