2
WORKING
Bars
PRESSURE
kPa
1.7
2
2.4
3
3.5
3.8
175
200
240
310
345
380
To check water
pressure, attach a
pressure gauge
to the outside tap
nearest the water
meter or water source.
A pressure gauge can
be obtained from your
local Hunter dealer.
Sprinkler System Design Capacity
Working Pressure
Design Capacity
Enter Static Pressure Here:
Enter the Size of the Meter Here:
Write the Service Line Size Here:
L/MIN
BARS KPA
Service lines are based on 30 meters of thick walled PVC. Deduct 7.6 l/min for copper pipe.
Deduct 19 l/min for new galvanized pipe.
Working pressure is the approximate working pressure at the head, and should be used only as a
guide when choosing the proper sprinkler heads and designing the system. The numbers in the
Design Capacity Chart are based on generally accepted flow rates (velocity). In some cases, de-
signers increase the velocity in copper pipe only from the accepted 2.3 meters per second (mps)
to 2.75 meters per second (mps). If you do not deduct the 7.6 l/min for copper pipe, the rate
is approximately 2.7 meters per second (mps). The friction loss is substantially increased at this
speed, and the working pressure will be affected. In order to use numbers in the chart, the length
of copper service line should not exceed 15 meters if you decide not to deduct the 7.6 l/min.
ServiCe line Size
APPrOXiMATe
STrinG lenGTH
7 cm
8.25 cm
9 cm
10.5 cm 11 cm 13.5 cm
Size of Copper Pipe
20 mm
25 mm
32 mm
Size of Galvanized
Pipe
20 mm
25 mm
32 mm
Size of PVC Pipe
20 mm
25 mm
32 mm
SPrinkler SySTeM DeSiGn CAPACiTy
STATiC Bars
PreSSUre kPa
2
200
2.8
275
3.5
350
4
415
4.8
480
5.5
550
WATer
MeTer
ServiCe
line
MAX
l/min
MAX
l/min
MAX
l/min
MAX
l/min
MAX
l/min
MAX
l/min
15 mm
13 mm
20 mm
25 mm
7.6
15
15
15
23
26
19
30
30
23
30
38
26
38
49
26
45
57
20 mm
20 mm
25 mm
32 mm
15
19
19
23
26
45
30
38
64
34
53
76
38
64
83
45
76
83
25 mm
20 mm
25 mm
32 mm
15
19
19
26
30
53
30
53
91
34
68
98
45
76
114
45
76
130
B. Determine System Design Capacity
When planning an efficient automatic irrigation system, you must
first determine the correct Sprinkler System Design Capacity –
how much water is available for irrigation.
If the system will be installed using the city water supply, follow
steps 1 – 3 below. If the water will be drawn from a lake, tank,
bore hole or well, your Hunter dealer or the pump installer will
have the specifications for pressure and volume output of your
pump. Enter this information in the Working Pressure and Design
Capacity boxes at the bottom of the page.
1. Water Pressure (kPa) (Bars)
To check the water pressure, attach a pressure gauge to the
outside tap closest to the water supply. Make sure that no other
water is flowing at the residence. Turn on the tap and record the
number in the area provided to the right. This is the static water
pressure in kPa or Bars.
2. Water Volume (l/min)
To determine the volume of water available for the system, you
need two pieces of information:
A. What size is the water meter or water supply line?
Water meters will generally have the size stamped on the
meter body. The most common sizes for residential meters
are 15 mm, 20 mm, and 25 mm. In some areas the water
supply hooks directly into the city main without the use of
the water meter. In these cases, simply enter the size of the
service line in the space provided.
B. What size is the service line?
Measure the outside circumference of the pipe that runs
from the city main to the house. An easy way to do that is to
wrap a piece of string around the pipe, measure the string,
and use the table to the right to convert the string length to
pipe size.
3. System Design Capacity
Using the System Design Capacity Chart on this page, locate
the three numbers you just recorded to determine the Sprinkler
System Design Capacity in liters per minute (l/min). Record
this number in the l/min box. Next, locate your system’s static
pressure and move down that column and find the system’s
working pressure; record it in the kPa/Bars box. Working pressure
will be used when choosing sprinkler heads and designing the
system.
You have now established the maximum l/min and the
approximate working pressure available for the sprinkler system.
Exceeding these maximums may result in inefficient watering or a
condition referred to as water hammer, which could cause serious
damage to the system. These two numbers will be used in the
design process.
