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Sprinkler GPM
02/09/12
As we saw previously, the flow rate in gallons per minute (GPM) of each sprinkler
head is determined by the nozzle installed in the head. It is necessary to know
the GPM for each head in order to determine which heads will be connected to
each valve and in order to determine the size of each pipe in the sprinkler
system.
You will probably need to dig up the sprinkler manufacturer's literature again.
In the literature the manufacturer shows different GPM and radius information
for each sprinkler nozzle based on the operating pressure (PSI). Now we can
use that information to find the GPM for each sprinkler head. First, determine
what the SPACING is between each head and the others around it. Next, look for
the radius closest to that spacing and use the corresponding GPM as the flow
for the head.
Write down on your plan the GPM for each sprinkler next to the sprinkler symbol.
Hint: If you're a tutorial supporter you will find the GPM and radius data for
many of the popular sprinklers in the Bonus Section.
Example: You note that a spray type head on your plan is a 1/2 circle pattern
and the distance to the 3 closest adjacent heads are 13 feet, 12 ft., and 14
ft.. So the spacing for this head is 14 ft. (the highest of the 3). Looking
at the manufacturer's literature you note that a radius of 14 ft. for the 1/2
circle nozzle in this sprinkler requires a pressure of 25 PSI and a flow of
1.65 GPM. Write down the flow of 1.65 GPM next to the sprinkler head on your
drawing. You then repeat this procedure for each sprinkler head on your drawing.
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