2.1 Sprinkler and Nozzle (Emitter) Condition

The sprinkler (or drip emitter) is the last point of application control! Regular inspection of the system should be done on a weekly inspection of the crop. Damaged or malfunctioning sprinklers or clogged nozzles require correcting the situation. Maintenance includes replacing damaged sprinklers with identical new components, ensuring that vegetation does not grow in the water throw path, and verifying that the controller is operating for the correct time period for water application. Figure 2.1a illustrates an impact sprinkler head and shows the nozzle.


Figure 2.1a. Sprinkler components should be inspected. Shown is a plastic sprinkler and plastic nozzle. Rotation components and nozzle condition should be checked.

As a system ages there is opportunity for the grit in the irrigation water to wear the nozzle opening and cause it to become larger. A larger opening requires more water at a given pressure to function. If the increased water flow is not available from the pump, then the pressure will drop at the nozzle because there is less resistance to flow. The accumulative effect of extra flow through enlarged nozzles is a change in the system dynamics and performance. The system may not look any different to the eye.


Drill bits with nozzle

Figure 2.1b. Use a set of inch unit or metric unit drill bits as appropriate to match the nozzle sizes. Drill bits shanks of the nozzle size or larger are required. Note shank in the nozzle. Select size and fit to a new nozzle first.

To test for nozzle wear, get a new nozzle of the correct diameter and get drill bits that are the same size and slightly larger and slightly smaller than the new size. The sizes should be within a few thousands of an inch or mm of each other. Test the drill bits carefully on the new nozzle to get a feel for the fit without damaging the nozzle.

Figure 2.1b illustrates a set of drill bits and shows a drill shank in the nozzle to check size. Next, test several used nozzles to see what size they are. Compare the measurements to other nozzles in a catalog to try to determine the difference in specs and flow rates. A 10% or greater variation from the new one suggests a problem. Figure 2.1c. illustrates the normal nozzle flow to be expected on a irrigation lateral by good design procedures.

Nozzle Uniformity Graph

Figure 2.1c. Check nozzle wear carefully using drill bit shanks. First, fit the drill shank to a new nozzle and then check old nozzles for wear. Wear will gradually cause increased non-uniformity of the water application.


An alternative might be to collect the flow from the used nozzle for one minute or more in a container and then measure the volume. Calculate the flow rate in gallons per minute. Compare the discharge of nozzles at the beginning of the lateral to one at the end of the lateral.

A new nozzle could be installed and the system operated to collect discharge from it for one minute or more on the same lateral. Do this test at the beginning and at the end of a lateral. Compare these flow rates to get a percent difference. However, with worn nozzles in the irrigation zone, the pressure may not be what it should be and the results will not represent performance with all new nozzles.

Install new nozzles if the wear is excessive. New nozzles may bring the system closer to the original specs. Pump wear or other problems may be additional problems.

Nozzles may have been replaced by the wrong size nozzles at some previous time. Check nozzle specs or system specs to be sure the correct nozzle diameter is in place. The tests above should indicate a problem if the wrong nozzles are in use.

Drip emitters have been known to clog, leaving a plant without water. While new designs have reduced this problem, the drip emitter requires clean water and the emitter may clog from dirt or organic material in the water. Algae may be growing in the pipe lines and can be flushed to the emitter.