Compare Site Information to Criteria
1. Do the heads have head-to-head coverage? (Does
one head spray all the way to the next head? I.e. it does not
spray less than or greater than the spacing between heads.)
If YES, go to Step 2. If NO, go to Step 3.
2. Do you have access to the manufacturer’s sprinkler nozzle data?
If YES, go to Process 1. If NO, go to Step 3.
3. Do the heads produce a lot of misting spray (a sign of too much
pressure)?
If YES, go to Process 3. If NO, go to Step 4.
4. Is the system less than 10 years old?
If YES, go to Process 2. If NO, go to Process 3.
Process 1: Manufacturer’s Charts and PR (precipitation rate) Calculations
1. Determine if the head layout is in a square or triangular pattern.
2. Verify that you have head-to-head coverage and the nozzles are
installed for matched precipitation, a general rule of thumb is: as
the spray arc doubles, so should the flow.
3. You can use the manufacturer’s PR rates if you have fixed spray
nozzles within the same radius family, or rotors/impacts that are
all 180 degree arcs with the same nozzle.
4. If you have matched PR nozzles, use this formula for square
spacing:
PR = [GPM (for any arc)
x
34,650] ÷ [Degree of Arc
x
Head
Spacing (ft.)
x
Row Spacing (ft.)]
For triangular space:
PR = [GPM of 360 Arc
x
96.25] ÷ [Head Spacing (ft.)
x
Head
Spacing (ft.)
x
.866]
Site Data Gathering98
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