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Landscape Irrigation. 2005 Commercial Horticulture In-Service . Slide Set and Narrative Provided by Dr. Brian G. Leib Dr. John Buchanan Biosystems Engineering & Environmental Science. Agricultural Extension Service. The University of Tennessee. Design and Management Factors.

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Landscape irrigation l.jpg

Landscape Irrigation

2005 Commercial Horticulture In-Service

Slide Set and Narrative Provided by

Dr. Brian G. Leib

Dr. John Buchanan

Biosystems Engineering & Environmental Science

Agricultural Extension Service

The University of Tennessee


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Design and Management Factors

  • 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


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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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Rivers and Lakes may provide a Non Limiting Supply

Creeks and Ponds; however, may Constrain the Landscape Irrigation System to Supply Limitations

Surface and Ground Water Sources


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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?

  • 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-to-head 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.


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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 > 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 Equipment

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 Rule EquipmentClass 160 PVC Pipe

Size in InchesFlow (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


Pipe size in a zone mainline based on 5 gpm per sprinkler l.jpg

M Equipment

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’

40 gpm

1. Corp.

Valve

3. Water

Meter

6. 1.5’

Diaphragm

Valve

7. 1.25”

20 gpm

15 gpm

8. 1”

11. ¾” or ½”

Swing Joint

10 gpm

9. 1”

10. 1”

5 gpm


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Backflow Prevention Equipment

  • 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 Equipment

  • 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) Equipment

  • 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 Equipment

  • 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) Equipment

  • 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 Equipment

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


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Controller Settings and Irrigation Scheduling Equipment

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 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



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Resources Equipment

  • 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


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