Landscape Irrigation

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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

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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

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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

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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

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Municipal Water Sources

• Utility Water and Well Water usually constrain
  the flow available to a Landscape Irrigation
  System

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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

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Pressure and Flow Rate
Pressure and Flow Rate are Related (pressure vs.
flow rate is different for every system)
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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

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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

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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

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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

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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
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Sprinkler Overlap For Uniformity
Distance between Sprinklers Radius of Throw
Head-to-Head Spacing 1. Good Uniformity
2. Good Economics
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Rules for Spacing Sprinklers.
Are most landscape areas simple squares and
rectangles?

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 dont leave a big gap in
   one area to make the rest of the area even.

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Example Landscape Sprinkler Layout
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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 gt 12 gpm, a
severe pressure drop will occur.
20 psi
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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
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Sizing Pipe with a Velocity Method
Flow is Q 20 gpm
V 5.71 ft/sec FL 4.59 psi/100
V 2.65 ft/sec FL 0.71 psi/100
1 pipe
1.5 pipe

• 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
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Simplified Pipe Chart based on 5 ft/sec
RuleClass 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

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

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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

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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

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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

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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 feet2
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
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Controller Settings and Irrigation Scheduling
Precipitation Rate
Z 1 1.0 in/hr Z 2 0.5 in/hr Z 3 1.0 in/hr
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 1000 1030 2 60 min 1030 1130
3 30 min 1130 1200 4 15
min 1200 1215
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Uniformity Impact on Operating Cost
Six inches of water required on a half acre lot Six inches of water required on a half acre lot Six inches of water required on a half acre lot
Municipal Water Cost of 0.61/100gal Municipal Water Cost of 0.61/100gal Municipal Water Cost of 0.61/100gal
Driest 10 receives 66 of requirement Driest 10 receives 66 of requirement 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
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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
• Orthos 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