Is sand media your filter station?
If sand media is the filter station in the system, when there is no pressure on the system and during safe conditions, open up the tanks and check the sand level and the texture of the sand. Once the sand starts to lose its sharp edge feel, the performance will start to degrade. Each tank should have a level indicator on the outside for visual measurement.
water meters – For a water meter to work properly, it is important to make sure that the recommended pipe diameters before and after the meter are accomplished correctly and that sufficient air venting is installed upstream from the meter. This should be done during the installation of the system. Sometimes meter readings will read low if there is debris stuck in the impeller, slowing its rotation. A quick check of this can be done by taking the water meter head out and inspecting it visually.
Mainline pipe network
It is good practice to flush mainline pipes several times during the season to remove any debris that has settled out in the pipes. In most all agricultural systems, some debris (usually 6-15 percent) will get past the primary filter station and make it downstream. This debris will typically settle out in pipes where the velocity is low toward the ends of the lines. When flushing
Typical flushouts for mainline and submain pipes Drip line laterals
The end of a drip line is the most susceptible location for the debris, as it is literally the end of the irrigation system. Two things should be accomplished when doing seasonal maintenance. First, check the pressures at the extreme end of the line and compare with the expected pressures from the design. This will help ensure that the system is achieving the expected flow rates. The second task is to flush the laterals to remove any debris that made it through the mainlines and submains. The protocol would be exactly the same as the mainline and submain examples above.
By taking this step-by-step approach, you are on your way to a cleaner system that will last longer and perform as it was designed while protecting your initial investment for years to come.
Mike Illia is the senior product manager for Netafim Irrigation Inc. He earned a bachelor’s degree in agricultural engineering in 1992 and has spent 26 years working in the ag irrigation industry.
22 Irrigation TODAY | October 2018
the lines, slowly open the flushout valves (almost all systems will be designed with strategic flushing locations) and allow to run for several minutes before closing slowly. Closing fast will induce unwanted water hammer. During this time, you will see the water start clear, turn dirty and then turn clear again. This should happen several times during those few minutes the valve is open.
Block valves & submains
In most irrigation system designs, the designer will precisely specify an area to receive a specific downstream pressure (e.g., 30 psi downstream of the valve for permanent crop applications, or 15 psi downstream for thinwall drip line applications). All that is needed is to verify that the pressure is still at the designed pressure. In many cases, this pressure might have been modified during the season. The pipes downstream of the valve supplying the irrigation block (submains) will need to be flushed in the same fashion as described in the “Mainline pipe network” section.
Photo credit: Mike Illia
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