Because it can be unpleasant to be sprayed with water, irrigation should be done when people and pets are not present. Early in the morning (4:00-5:00 a.m.) is a good time to run the system, since irrigating late at night may lead to the growth of fungi and promote turf disease. Since wastewater is generated every day, the system should run every day. The run duration depends on the flow rate of the sprinkler heads in the system. Two important conditions are necessary when programming the controller.
If Steps 1, 2, and 3 were completed properly, these two conditions will occur simultaneously.
If the irrigation system is designed for “matched precipitation rates,” all zones will run the same length of time. If the zones are not matched, the run times should be programmed accordingly to assure that the wastewater is applied evenly.
Calculating the “precipitation rate” will provide the proper run time for the system. The precipitation rate (PR) for an individual sprinkler, a zone, or an entire sprinkler system is the depth of water applied in a given area, expressed in inches per hour. The PR of a zone is determine by multiplying the total gallons per minute of the zone by 96.25 and dividing by the total area the zone covers:
PR = GPM applied X 96.25 ------------------- area covered
Use the precipitation rate to determine the run time of the zone. If the PR is 1 inch per hour, the run time would be 0.2 of an hour or 12 minutes. Check the system with rain gauges and make adjustments as needed.
Zone 1
Flow rate = 9.6 gpm (2.4 + 4.8 + 2.4)Area = 1444 sq ft (76 x 38/2)
PR = 9.6 gpm x 96.25 = 0.64 in/hr
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1444 sq ft
96.25 is a conversion factor that converts cubic inches of water into inches per square foot per hour.
Run time = 0.2 in x 60 mins = 18.75 mins
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0.64 in/hr 1 hr
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