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# Sprinkler Precipitation Rates

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### Sprinkler Precipitation Rates

1. 1. Sprinkler Precipitation Rates
2. 2. What is Precipitation Rate <ul><li>The rate that sprinkler heads apply water to the soil or turf </li></ul><ul><li>The PR (Precipitation Rate) should be as consistent as possible throughout a zone </li></ul><ul><li>Avoid over or underwatering </li></ul>
3. 3. How to get Matched PR <ul><li>Use sprinkler heads with the same precipitation rates (matched PR’s) </li></ul><ul><li>Use only heads of the same type </li></ul><ul><li>Use only heads from one manufacturer </li></ul>
4. 4. Calculating PR using Total Area Method <ul><li>Measured in inches of water applied per hour to the irrigated area </li></ul><ul><li>Formula for the total area </li></ul><ul><ul><li>PR = 96.25 x Total GPM </li></ul></ul><ul><ul><li>Divided by Total Area in square feet </li></ul></ul><ul><li>96.25 is a constant </li></ul>
5. 5. Sample Problem <ul><li>Area is 60 ft x 15 ft with the following heads </li></ul><ul><ul><li>6 half circle (1.0 GPM nozzles) </li></ul></ul><ul><ul><li>4 quarter circles (.5 GPM nozzles) </li></ul></ul><ul><li>1. Total GPM = (6 x 1.0) + (4 x .5)= 8.0 GPM </li></ul><ul><li>2. Total area = 60 x 15 = 900 sq. ft. </li></ul><ul><li>3 PR 96.25 x 8/900 = .86 inches/hour </li></ul>
6. 6. Calculating PR using Individual Head Method <ul><li>For square pattern </li></ul><ul><ul><li>PR = GPM for full circle sprinkler x 96.25 / spacing 2 (S X L) </li></ul></ul><ul><ul><li>This means if you have all half sprinklers double their GPM to get the rate for a full circle </li></ul></ul><ul><li>For triangular pattern </li></ul><ul><ul><li>PR = GPM of full circle sprinkler x 96.25 / spacing 2 x 0.866 </li></ul></ul>
7. 7. Example <ul><li>The rows are 25 feet apart and the sprinklers are 30 feet apart in the row. </li></ul><ul><li>The heads are arranged in a triangle pattern. The heads use 6 GPM. </li></ul><ul><li>(6 x 96.3) / [(25 x 30) x 0.866] </li></ul><ul><li>577.8 / [750] x 0.866 </li></ul><ul><li>577.8 / 649.5 </li></ul><ul><li>0.89 inches per hour </li></ul>