1. Landscape Irrigation
Agricultural Extension Service
The University of Tennessee

2. *Design and Management Factors
1. Water Supply Requirements and Limitations
2. Scale Drawing of the Site
3. Sprinkler/Drip products that Match the
Landscape
4. Spacing of Sprinklers
5. Sprinkler Zones
6. Pipe Sizing
7. Irrigation System Equipment
8. Programming an Irrigation Controller

3. How Much Water is Required?
 0.7 inches per week 2.0 gpm/ac in 24hr/da
 1.0 inch per week 3.0 gpm/ac in 24hr/da
 1.5 inches per week 4.5 gpm/ac in 24hr/da
 Irrigate all at one time 80 gpm/ac in 2 hr/day
 Allows some flexibility 15 gpm/ac in 7 hr/da

4. *Surface and Ground Water Sources
 Rivers and Lakes may
provide a Non Limiting
Supply
 Creeks and Ponds;
however, may Constrain
the Landscape Irrigation
System to Supply
Limitations

5. *Municipal Water Sources
 Utility Water and Well
Water usually constrain
the flow available to a
Landscape Irrigation
System

6. Measuring Flow and Pressure
 Example - Measuring
the flow and pressure
from a residential
hydrant
 connection to hydrant
 tee fitting
 pressure gauge
 ball valve
 5 gallon bucket & stop
watch or municipal flow
meter

7. Pressure and Flow Rate
0
20
40
60
80
100
120
0 2 4 6 8 10 12 14
Flowrate (gpm)
Pressure(psi)
Pressure and Flow Rate are Related
(pressure vs. flow rate is different for every system)

8. *Proper Equipment: Rotating Sprinklers
 A single sprinkler can
cover a large area, 20 to
60 foot radius
 Needs a higher flow rate,
0.5 to 20 gpm
 Needs higher pressure,
35 to 75 psi
 Sprinklers are “constant
discharge” and do not
automatically provide
“matched precipitation”
when part-circles are
used

9. *Sprayer Sprinklers
 Wets a smaller area, 8 to
16 foot radius
 Smaller water flow, 0.25
to 4 gpm
 Less pressure required,
20 to 40 psi
 Can wet rectangular
areas
 Automatic “matched
precipitation when part-
circles sprinklers are
used

10. *Bubblers
 good applications in plant
beds
 wets a small area
 low pressure requirement,
15 to 30 psi
 low flow rate, 8 gph to 2.5
gpm

11. *Drip Emitters and Dripline
 Good applications in plant
beds and vegetable and
fruit gardens
 very low flow rate, 0.5 to 2.0
gph
 very low pressure, 10 to 25
psi (pressure compensating
emitters are designed for a
greater pressure range)
 direct application of water to
root zone of individual
plants
 water must be very clean to
prevent clogging of emitters

12. Ideal Pressure and No Wind
How Much Water in the Cans?
Even in all cans
More in cans closer to the sprinkler
More in cans further from the sprinkler
*Uniformity of Water Caught in Cans
around a Single Sprinkler

13. *Sprinkler Overlap For Uniformity
Distance between Sprinklers
=
Radius of Throw
Head-to-Head
Spacing:
1. Good Uniformity
2. Good Economics

14. *Rules for Spacing Sprinklers.
1. Pick a sprinkler with a wetted radius that is as large as possible and
does not greatly exceed the shortest distance across the area.
2. Place part-circle sprinklers at all corners
3. Place part-circle sprinklers at an even spacing on the edges between
corners using head-to-head spacing as a guide.
4. Place full-circle sprinklers in the interior area using the same head-to-
head spacing used on the edge sprinklers.
5. Perfect head-to-head spacing is impossible in most cases. It is O.K. to
stretch and/or crowd the spacing by 10%.
6. Adjust the sprinklers to even out the spacing over the entire area and
don’t leave a big gap in one area to make the rest of the area even.
Are most landscape areas
simple squares and rectangles?

15. Example Landscape Sprinkler Layout

16. *Zones Avoid Excess Flow Demand
A Zone is a group of sprinklers that operate together on the
same lateral pipe network downstream from a common valve.
Limited Flow Rate of 12 gpm at 45 psi and sprinklers that require 3 gpm
8 sprinklers x 3 gpm/spr = 24 gpm > 12 gpm,
a severe pressure drop will occur.
20 psi
20 psi

17. *Zones Allow Equal Application of Water
from Different Equipment
Rotating Sprinkler, Full Circle – 0.25 in/hr
Sprayers: Full, ½, & ¼ Circle – 1.5 in/hr
Rotating Sprinkler, Half Circle – 0.5 in/hr
Rotating Sprinkler, Quarter Circle – 1.0 in/hr
Drip – 0.1 in/hr

18. Sizing Pipe with a Velocity Method
Flow is Q = 20 gpm
1.5” pipe
1” pipe
Proper pipe sizing will reduce friction loss, improve uniformity, save material
costs, lower pumping costs and control waterhammer.
Velocity Method
• Locate pipe network for irrigation system.
• Determine the flow in each section of pipe.
• Determine the smallest size pipe that keeps flow
velocity below 5 feet per sec (fps)
Pipe charts are available in most Irrigation Supply Catalogs
V = 2.65 ft/sec
FL = 0.71 psi/100’
V = 5.71 ft/sec
FL = 4.59 psi/100’

19. Simplified Pipe Chart based on 5 ft/sec Rule
Class 160 PVC Pipe
Size in Inches Flow (gpm)
1 1 – 15
1 ¼ 16 – 28
1 ½ 29 – 37
2 38 – 59
2 ½ 60 – 85
3 86 – 130
4 131 – 200
5 201 – 325
6 326 – 450

20. S M
Source
1. Corp.
Valve
2. Gate
Valve
3. Water
Meter
4. Backflow
Preventor
5. 2” PVC
Mainline
200’
6. 1.5’
Diaphragm
Valve
7. 1.25”
20 gpm
8. 1”
9. 1”
10. 1”
40 gpm
15 gpm
10 gpm
5 gpm
11. ¾” or ½”
Swing Joint
POC
Pipe Size in a Zone & Mainline Based on 5
gpm per Sprinkler

21. Backflow Prevention
 If you use utility water
 you must have backflow
prevention installed
 prevents water from
flowing backwards into
the supply line in case of
pressure-loss from within
the system
industrial-sized
backflow prevention

22. *Swing Joints for Sprayers and Sprinklers
 Use a flexible
connector-piping from
lateral to sprinkler
 allows the sprinkler to be
set at the correct depth
and to be moved deeper
if the soil settles
 allows sprinkler to move
it run-over by tractor tire
 reduces damage to
lateral

23. *Valves for Irrigation Zones (sets)
 Valves off of the
mainline control
individual sets
 can be manual valves or
electric valves
 electric valves are
needed when using
timers

24. 24 V-AC Solenoid Valves
 Magnetic coil is used to
open a spring-loaded
valve
 very common application
 easy to rebuild or replace
 allows for manual
operation

25. *Controller (timer)
 Normal Program
 Days of the week to water –
MTWThFSaSu
 Start time during the day to
initiate the valve sequence
 Valve run time of each zone
(set)
 Special Features Available:
 Rain Delays
 Raingauge shutdown
 Soil sensor shutdown

26. Ar = 96.3 Q = Application rate in inches per hour
A
Q = Flow or discharge in gallons per minute
A = Area into which flow is applied in feet^2
Example: A full-circle sprinkler discharges 2.4 gpm and the
sprinkler spacing is 30 by 30 feet.
Ar = (96.3 x 2.4) / (30 x 30)
= 0.25 inches per hour
Application Rate – Flow into an Area

27. Z 1 1.0 in/hr
Z 2 0.5 in/hr
Z 3 1.0 in/hr
Precipitation
Rate
Precipitation
Rate
2.0 in/hr Z 4
Set Controller to apply 0.5 inches 2 days per week = 1 inch per week
Time for zone 1 = 0.5in / 1.0 in/hr = 0.5 hours or 30 min.
M Th
Valve Tz On Off
1 30 min 10:00 10:30
2 60 min 10:30 11:30
3 30 min 11:30 12:00
4 15 min 12:00 12:15
*Controller Settings and Irrigation
Scheduling

28. Uniformity Impact on Operating Cost
Six inches of water required on a half acre lot
Municipal Water Cost of $0.61/100gal
Driest 10% receives 66% of requirement
Uniformity Water Applied Irrigation Cost
inches
85% 6.0 $ 510.00
80% 6.2 $ 525.30
75% 7.2 $ 612.00
65% 10.8 $ 918.00

29. Resources
 Landscape Irrigation Design by Eugene W.
Rochester, ASAE Publication #8, 0-929355-61-X
 Simplified Irrigation Design by Pete Melby,
John Wiley & Sons, Inc., ISBN 0-471-28622-22
 Ortho’s All About Sprinklers and Drip
Systems, Meredith Books Inc, ISBN 0-89721-
413-7
 Drip Irrigation for Every Landscape and All
Climates by Robert Kourik, Metamorphic Press,
ISBN 0-9615848-2-3