Transcript Landscape Irrigation Commercial Hort

Landscape Irrigation
2005 Commercial Horticulture In-Service
Agricultural Extension Service
The University of Tennessee
Slide Set and Narrative Provided by
Dr. Brian G. Leib
Dr. John Buchanan
Biosystems Engineering & Environmental Science
Design and Management Factors
1.
2.
3.
4.
5.
6.
7.
8.
Water Supply Requirements and Limitations
Scale Drawing of the Site
Sprinkler/Drip products that Match the
Landscape
Spacing of Sprinklers
Sprinkler Zones
Pipe Sizing
Irrigation System Equipment
Programming an Irrigation Controller
How Much Water is Required?

0.7 inches per week
1.0 inch per week
1.5 inches per week
2.0 gpm/ac in 24hr/da
3.0 gpm/ac in 24hr/da
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
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
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
Municipal Water Sources

Utility Water and Well
Water usually constrain
the flow available to a
Landscape Irrigation
System
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
Pressure and Flow Rate
Pressure and Flow Rate are Related
(pressure vs. flow rate is different for every system)
120
Pressure (psi)
100
80
60
40
20
0
0
2
4
6
8
Flowrate (gpm)
10
12
14
Proper Equipment: Rotating Sprinklers


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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
Sprayer Sprinklers


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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 partcircles sprinklers are
used
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
Drip Emitters and Dripline


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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
Uniformity of Water Caught in Cans
around a Single Sprinkler
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
Sprinkler Overlap For Uniformity
Distance between Sprinklers
=
Radius of Throw
Head-to-Head Spacing:
1. Good Uniformity
2. Good Economics
Rules for Spacing Sprinklers.
Are most landscape areas
simple squares and rectangles?
1.
2.
3.
4.
5.
6.
Pick a sprinkler with a wetted radius that is as large as possible and
does not greatly exceed the shortest distance across the area.
Place part-circle sprinklers at all corners
Place part-circle sprinklers at an even spacing on the edges between
corners using head-to-head spacing as a guide.
Place full-circle sprinklers in the interior area using the same head-tohead spacing used on the edge sprinklers.
Perfect head-to-head spacing is impossible in most cases. It is O.K. to
stretch and/or crowd the spacing by 10%.
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.
Example Landscape Sprinkler Layout
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
20 psi
8 sprinklers x 3 gpm/spr = 24 gpm > 12 gpm,
a severe pressure drop will occur.
20 psi
Zones Allow Equal Application of Water
from Different Equipment
Sprayers: Full, ½, & ¼ Circle – 1.5 in/hr
Drip – 0.1 in/hr
Rotating Sprinkler, Half Circle – 0.5 in/hr
Rotating Sprinkler, Full Circle – 0.25 in/hr
Rotating Sprinkler, Quarter Circle – 1.0 in/hr
Sizing Pipe with a Velocity Method
Flow is Q = 20 gpm
V = 5.71 ft/sec
V = 2.65 ft/sec
FL = 0.71 psi/100’
1.5” pipe
1” pipe
FL = 4.59 psi/100’
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)
Proper pipe sizing will reduce friction loss, improve uniformity, save material
costs, lower pumping costs and control waterhammer.
Pipe charts are available in most Irrigation Supply Catalogs
Simplified Pipe Chart based on 5 ft/sec Rule
Class 160 PVC Pipe
Size in Inches
1
1¼
1½
2
2½
3
4
5
6
Flow (gpm)
1 – 15
16 – 28
29 – 37
38 – 59
60 – 85
86 – 130
131 – 200
201 – 325
326 – 450
Pipe Size in a Zone & Mainline Based on 5
gpm per Sprinkler
POC
Source
S
4. Backflow
Preventor
2. Gate
Valve
M
1. Corp.
Valve
40 gpm
3. Water
Meter
6. 1.5’
Diaphragm
Valve
11. ¾” or ½”
Swing Joint
5. 2” PVC
Mainline
200’
7. 1.25”
20 gpm
15 gpm
8. 1”
10 gpm
9. 1”
5 gpm
10. 1”
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
Swing Joints for Sprayers and Sprinklers

Use a flexible
connector-piping from
lateral to sprinkler
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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
Valves for Irrigation Zones (sets)

Valves off of the
mainline control
individual sets

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can be manual valves or
electric valves
electric valves are
needed when using
timers
24 V-AC Solenoid Valves

Magnetic coil is used to
open a spring-loaded
valve
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
very common application
easy to rebuild or replace
allows for manual
operation
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
Application Rate – Flow into an Area
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
Controller Settings and Irrigation Scheduling
Precipitation
Rate
2.0 in/hr
Z1
Z4
Precipitation
Rate
1.0 in/hr
Z2
0.5 in/hr
Z3
1.0 in/hr
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
1
2
3
4
Tz
30 min
60 min
30 min
15 min
On
10:00
10:30
11:30
12:00
Off
10:30
11:30
12:00
12:15
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
85%
80%
75%
inches
6.0
6.2
7.2
10.8
65%
Irrigation Cost
$
$
$
510.00
525.30
612.00
$
918.00
Resources
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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 0-89721413-7
Drip Irrigation for Every Landscape and All
Climates by Robert Kourik, Metamorphic Press,
ISBN 0-9615848-2-3