Calibrating a Sprinkler System

L.B. McCarty
Formerly Extension Turf Specialist
Environmental Horticultural Department
University of Florida
Gainesville, Florida 32611

Now with Clemson University

Calibrating or determining the amount of water your sprinkler system applies is an easy job. You can use the following procedure if you have an in-ground system or a sprinkler at the end of a hose.

Obtain several (5-10) coffee cans, tuna fish cans, or other straight sided containers to catch the irrigation water. Container which are 3 to 6 inches in diameter work the best.
If you have an in-the-ground system, place the containers in one zone at a time. Scatter the cans at random within the zone. Repeat the entire procedure in every zone because there may be differences in the irrigation rates.
Or, if you have a hose-end sprinkler to water your turf, place the containers in a straight line from the sprinkler to the edge of the watering pattern. Space the containers evenly.
Turn the water on for 15 minutes.
Use a ruler to measure the depth of water in each container.
NOTE: The more precise your measurement, the better your calibration will be. For most cases, measurements to the nearest 1/8 inch are adequate.
Find the average depth of water collected in the containers (all up the depths and then divide b y the number of containers).
To determine the irrigation rate in inches (centimeters) per hour, multiply the average depth of water times four.
That is all there is to calibrating your sprinkler system!

Now that you know your sprinkler system irrigation rate, you can more efficiently apply water to your turf. Use the table in this section as a guide for sprinkler times. For example, if the sprinkler system applies water at the rate of 2 inches per hour, and you wish to apply 0.75 inches of water, then you need to run your sprinklers for about 23 minutes. To calculate the time of irrigating for rates not listed in the table use the following equation:

     Minutes required  =  Amount of water  X  60 Your calibrated 
     to run each zone       to be applied         Irrigation Rate
          -------------------------------------------------------
                Irrigation Rate (amount of water/hour)
          -------------------------------------------------------
              0.5 in.       1.0 in.       1.5 in.        2.0 in.
              1.3 cm.       2.5 cm.       3.8 cm.        5.0 cm.
------------------------------------------------------------------------
Amount of water          Minutes to Run Each Zone
to be applied
------------------------------------------------------------------------

0.25in.                      30          15          10           8
0.6cm.

0.50in.                      60          30          20          15
1.3cm.

0.75in.                      90          45          30          23
1.9cm.

1.00in.                     120          60          40          30      
2.5cm.
------------------------------------------------------------------------

Calibration Pointers

Try to calibrate the sprinkler system during the same time the system is normally run, so that the water pressures are similar.
Low water pressure can significantly reduce the amount and coverage of water applied by a sprinkler system.
Never apply more than one inch of water per irrigation. Set time clocks on automatic sprinkler systems or time manual systems for applying the proper amount of water.
Most time clocks can be adjusted for more accurate time settings. Consult your local sprinkler company for details.
If you use a hose-end sprinkler, a mechanical timer and shut-off switch that attaches to the faucet will help make watering more efficient.
Avoid mixing sprinkler head types. Mist heads apply more water than impact heads. Match sprinkler heads for uniform coverage.
Check the sprinkler system frequently. Replace broken sprinkler heads, clear clogged nozzles and adjust the direction of a spray.
For more specific information on turf irrigation, see the watering section.
Use water efficiently; do not waste it!

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