®
SECTION 5 WEATHER
making
since 1986
water work
•
How to calculate Station Flow rates by
Measuring Station Flow Rates:
The second method may provide more accurate
results, by using the irrigation system’s water meter
to calculate flow rates. Use the following procedure:
o
Determine the units used by the water
meter (Gallons, cubic feet, etc.) Make
sure no other water will be flowing while
you are measuring flow rates. Also, if
there is more than one water meter
connected to the mainline, all of them
must be turned-off except the one you
are using to measure flow with.
o
Before beginning, turn on each station
to make sure there are no broken heads
or pipes which will cause incorrect flow
readings.
o
Begin by turning on a station long
enough to purge all of the air out of the
system. Then simultaneously, make
note of the meter reading and start
timing using a stopwatch. After 3
minutes has elapsed make note of the
water reading again. Subtract the
starting meter reading from the ending
meter reading, this will give you the
amount of water used by the valve in 3
minutes. Continue this procedure until
all stations have been measured.
o
To calculate the flow rate, divide the
amount of water the station used
(measured in gallons) by 3 minutes, this
will give you the station’s flow rate
measured in GPM’s.
Example #1
(if water meter units are in gallons):
The starting meter reading is 312,121 After 3
minutes the ending meter reading is 312,378
gallons, the flow rate would be calculated as follows:
312,378 gallons – 312,121 gallons = 257 gallons
257 gallons ÷ 3 minutes = 85.6 GPM
Example #2
(If water meter units are in cubic feet or CF):
The starting meter reading is 9,975 CF after 3
minutes the ending meter reading is 10,003 CF the
flow rate would be calculated as follows:
10,003 CF-9,975 CF = 28 CF
28 CF x 7.48 gallons = 209.4 gallons
(1 CF = 7.48 gallons)
209.4 gallons ÷ 3 minutes = 69.8 GPM
Example #3
(if water meter units are in hundreds of cubic feet or
CCF):
The starting meter reading is 12,321 CCF after 3
minutes the ending meter reading is 12,321.25 CCF,
the flow rate would be calculated as follows:
12,321.25 CCF – 12,321.00 CCF = .25 CCF
.25 CCF x 748 gallons = 187 gallons
(1 CCF =748 gallons)
187 gallons ÷ 3 minutes= 62.3 GPM
FLOW METER INSTALLED
D
6. Station flow rates & Area with flow meter
installed.
From the MAIN MENU screen.
1.
Press the
PROGRAMS & STATIONS
Menu key.
2.
Press the
STATIONS
Menu key.
3.
Press the
STATION UP
or
STATION
DOWN
keys to select the station
desired.
The STATION PROGRAMMING screen is displayed
(Figure 5.26).
STATION PROGRAMMING
Station 1 . . . . . . . . . . . . . . PROG A
Last Min : 2.3
Estimated Mins : 3.2 % of ET : 100 %
Mins per Cycle : 4
Soak-in Time : 5 No Water Day 0
Expected Flow = 25 GPM
Area = 3826 sq / Ft
Precip = 0.63 In / Hr
Test
Figure 5.26
