For a sprinkler system, broken components, unevenly spaced sprinkler heads, tilted risers and dissimilar heads or nozzles are common problems in overhead irrigation systems. In drip systems, plugged emitters, broken tubes, out-of-place emitters and incorrect pressures are problems to be found.
As said earlier, pressure gauges and flow meters are two important tools for monitoring an irrigation system. It is recommended that systems without them have them installed. Pressure gauges should be located at the pump, before and after filters, and in each irrigation zone after any pressure regulators, valves, or other devices. Another rule of thumb is to put an additional one at the high and/or low point of the system (high/low elevation) on the property, at least to record the elevation change in pressure. A flow meter that records the total volume of water pumped, in gallons, or a combination current flow, in gpm, and total recording meter is also a good monitoring device. A current flow meter, in gpm, gives a base flow value to monitor for any irrigation zone.
A pressure and flow check should be done. Manual and electrical valves should be inspected for leaks and to see that they are working. Check the controller settings for each zone. Look at the water pressure to see if the gauge is working and that the pressure reading appears to be correct. Make notes on what you observe. Check to see if the pressure is indeed correct. Incorrect pressures mean a distorted distribution pattern for sprinklers and emitters alike.
Sprinklers or drip emitters – Pressure and Flow Rate
A systematic check of pressures and flow discharge throughout the system will give an indication of the functioning of sprinklers and emitters. Check the pressure. A portable pressure gauge with a pitot tube attached allows measurements at the sprinkler nozzle or by inserting into a drip line. A connection point can be made with a valve to close it when a pressure gauge is not attached. This allows a valve to be moved around to check the pressure. Record the location and the measured pressure.
Check the flow rate at several nozzles by collecting the discharge for a given time, maybe one minute, at each nozzle and measure the volume with a graduated cylinder or marked measuring container. Record the nozzle location and its flow rate.
A discussion of pressure and flow is given earlier in Section 2.0 to help one understand the pressures and flows to expect.
Inspect for damage. Aluminum lines can be partially crushed by equipment and plastic pipe can be cracked or broken by equipment. In the northern areas, freezing of water filled pipes can result in broken pipelines to be found in spring. Flush pipelines to remove debris that has settled on the bottom.
Valves can be only partially open or damaged by freezing. A valve that does not function properly will affect performance. An electric valve that is not closed will affect pressure in the entire system.
Controller, pressure gauges and flow meters
Controllers are set to specific irrigation run times and they cycle through irrigation zones. Check the settings to see that they are correct. Be sure that pressure gauges and flow meters are operating correctly. Calibrate the meters for accuracy.
Filters gradually clog and should be cleaned or set for automatic backflushing. Inspect the filter for integrality.
Vacuum Relief Valves
Vacuum relief valves are located at high points in an irrigation system to vent air that is trapped in the pipeline. This air might cause a blockage of flow over a high point. Also, the vent allowed air to enter the line when it drains so that there is no vacuum created in the pipeline to cause drip emitters to pull dirty water into the emitters. If the vacuum relief valve is leaking, then dirt or debris may be holding the valve partially open. The valve has a ball that is pushed up by water to close the vent or drops to allow air to enter.