Civil Engineering Chapter 20 Homework Trenches Exit The Valves And Return Below

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Exercise 20

Irrigation System

Installation

OBJECTIVE

TEXTBOOK REFERENCE

Information related to this activity can be found in the

INTRODUCTION—PART A: SPRAY

IRRIGATION SYSTEMS

Irrigation systems provide water for plant growth in all

types of landscape settings. Effective irrigation systems

begin with the careful design and planning of the entire

installation. Considerations that must be incorporated

into the design of an irrigation system include:

must provide adequate pressure and volume

to deliver the required amount of water to all

zones in the system. Large sites often require the

creation of zones simply to provide for ample

water pressure and volume throughout the site.

• Installation of a backflow prevention device.

to prevent contamination of the water source

to which the system is connected. All backflow

devices require that the mounting height of the

valve be above the highest irrigation head, with

switch that turns irrigation zones on and off.

This controller must be located with access

to power through a dedicated GFCI circuit,

easy connection to the irrigation system, and

a location where the system operator can gain

access for maintenance. Any sensors that monitor

or control the system must also be accessible to

the controller.

Connection to a water supply and electricity

source requires the assistance of a licensed

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78 Exercise 20 Irrigation System Installation

CAUTION

Trenching

Trenching for irrigation projects can be completed by

hand or with rented trenching machines. Excavate only

the amount of trench that will be worked on in any

given session. Excavation depths vary depending on the

Installing Wiring

After trenching is complete, install the control wiring from

the controller to the manifold or to each valve. Wiring

connections should be made using waterproof wire nuts

to reduce the chance of system failure due to corrosion.

Most wiring installations for irrigation are 18 gauge, but

14or 12gauge will carry more voltage.

Main Line Installation

Connecting pipes outside the trench makes for easier

work and reduces the possibility that foreign materials

will enter piping.

open flames, and work in a well-ventilated

location.

Manifold and Valve Installation

Systems may be designed to use a valve manifold situ-

ated in one location or valves that are positioned near

Valves that are distributed throughout the site are set

below grade and placed in valve boxes. To position and

assemble this type of valve, follow these steps:

• At each location where a valve is to be located,

excavate an opening the size of the valve box, plus

6 inches on each side and 4 inches below. The

location for the excavation should be centered

• Hold the valve in the desired location and mark

the main for trimming.

• Trim the main.

• If a sump has been installed, place a tee connected

to a ball valve drain directly over the sump. Add

6 inches of piping to the valve side of the tee. Glue

all fittings together.

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Exercise 20 Irrigation System Installation 79

Lateral and Riser Installation

From each valve location extends a network of pipes that

thread through the site or zone, connecting the valves

to each irrigation head location. These pipes are called

laterals. At each irrigation head location, a connecting

pipe called a riser runs from the lateral to the irrigation

head. Each lateral in an irrigation system typically has

several riser locations.

the valve at this time.

• When a riser location is encountered, cut the

lateral and glue a tee at the cut end. Verify that

the placement of the tee and riser will position

the irrigation head in the correct location without

twisting or bending the riser. Do not install the

head at this time. Risers can be a nipple (vertical

Valve Box Installation and Valve Wiring

• Place a valve box over the valve and seat the box

securely on the granular base.

• Verify that the controller wires are inside the valve

box.

• Cover any openings in the box by duct taping

heavy pieces of plastic to the outside of the box.

Standard riser

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80 Exercise 20 Irrigation System Installation

wiring schemes may be different, so verify the correct con-

nections on the wiring diagram.

Backfilling and Flushing

• Carefully backfill the irrigation lines to half to two

thirds full. Do not backfill around riser locations.

Do not compact the backfill at this time and avoid

stepping on the lines.

• Recap the risers and begin a second flushing,

this time going riser to riser and removing one

riser cap at a time. In each zone, first remove the

cap on the riser closest to the valve and flush for

2minutes, then recap the riser and repeat for the

next riser in line. Repeat for each riser in each

zone.

heads that project out of the ground, place a post or

#4 rerod next to the riser for stability. Bury the post

or rerod at least 2 feet into the ground.

PREREQUISITE EXERCISES

Students should have successfully completed Exercise

5, Tool Operation and Construction Techniques, before

completing this exercise.

• Access to water source using a 1/2 inch garden

hose and a GFCI duplex outlet

• One irrigation controller with a minimum of two

zones. Controller should be wired with a grounded

plug.

• 50 feet white 14 ga. irrigation controller wire

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Exercise 20 Irrigation System Installation 81

• Two valve boxes

• Three assembled swing ells with 1/2 inch Mips

• Two flexible risers with 1/2 inch Mips

• One fitting 3/4 inch S×S×S tee

• One reducing adapter 3/4 inch (slip end) to 1/2inch

(threaded end) SxFips (for hose connection)

• Assorted 1/2 and 3/4 inch threaded and slip

90 degree elbows, couplings, and caps

• Assorted waterproof wire nuts

• Joint tape

• 3 foot section of #4 rebar

• 5 pound sledgehammer

• Adjustable crescent wrenches

• Small table on which to set controller

EXERCISE DESCRIPTION—PART A

To complete this exercise, install the basic spray irriga-

Alternative Exercise

This alternative exercise provides practice in pipe cutting,

INTRODUCTION—PART B: DRIP IRRIGATION

SYSTEMS

Drip irrigation is an alternative to spray system irrigation

and uses water more efficiently. Drip systems are low-

pressure systems that precisely distribute water directly to

the root zone of plants rather than distributing water over

an entire planting area. Drip irrigation uses a variety of

water distribution techniques ranging from emitters that

slowly drip small amounts of water to micro-sprays and

ability to protect the system components from freeze is

difficult, and drip systems are more prone to plugging

and failure than sturdier spray systems. Unless placed

below soil surface, drip systems are not effective at water-

ing turf areas. Despite these limitations, the drive for

sustainability has increased the use of drip irrigation as a

method to reduce water consumption.

require a backflow preventer and pressure regulator. A

timer (usually battery operated) will be necessary if the

drip system is not on a spray system valve or the owner

does not want to manually operate the system. Each of

these fixtures is typically supplied with threaded fittings

that connect to the hose bibb/water line and each other

using typical plumbing connections (Figure 20–6). Also

each of the desired fixtures in line, and at the end

of this supply head, install a tubing adapter.

• The distribution line will slip into the compression

line is laid out along the paths that will best serve the

plant material being irrigated. For areas where the

distribution line does not come in contact with every

plant, branch lines of ¼“ connector tubing can sup-

ply water to additional plants. For smaller sites (50–75

emitters), a single distribution line can be split into

branch lines to better access the plant material. Large

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82 Exercise 20 Irrigation System Installation

5  Fipt

reducing

adaptor 5  MIPS

reducing

adaptor

5  5 90°

Valve Zone 2

Valve Zone 1

White and green

controller wires

Valve box

55 90°

elbow

Swing ELL

risers with

MIPS

55 Fips TEE

” PVC to

end of lateral

” PVC

to valve

555

TEE

Max. 20′

from valves

to controller

White

5  MIPS

adaptor

5 MIPS

adaptor

Water

source

hose

connection

Valve box

Notes:

-All pipe and fittings ” PVC from supply to valves

-All pipe and fittings ” PVC beyond valves

-Burial Depth 12″

Figure 20–5 Irrigation system exercise.

sites may require the creation of additional irrigation

heads and distribution systems to serve significant

Leave extra tubing to allow for adjustments in

alignment.

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Exercise 20 Irrigation System Installation 83

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84 Exercise 20 Irrigation System Installation

• If a system is installed on a sloping site, additional

pressure regulators may need to be installed in the

Emitters

Getting appropriate amounts of water to the plants in a

drip irrigation system requires choosing emission meth-

water over a given period of time. Typical emitters

provide ½ , 1, or 2 gallons of water per hour.

the distribution tubing can be routed next to or

through the plants being irrigated, distribution

tubing that has low-volume emitters placed

directly into the tube is available.

Flag emitters: flag emitters are drip emitters

• Micro-sprays. If a large number of low-growing

plants require irrigation and it is impractical to

route an emitter to each plant, micro-sprays can

distribute a low-volume spray similar to the heads

used in spray systems. Micro-sprays have a limited

volume and radius of spray, but can be useful in

small areas of ground covers and planting beds.

• Bubblers. For planting areas that are best irrigated

by flooding, bubblers can be installed on a drip

the distribution line or separated from the distribution

line through the use of ¼“ tubing.

Installation of emitters and/or ¼“ connection tubes

requires the use of a special tool termed a punch. The

punch is a small diameter awl that punches a hole

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Exercise 20 Irrigation System Installation 85

• Place the distribution tube on a solid surface and

hold a barbed connector with a pair of pliers.

• Use a twisting motion to push the connector

through the hole made by the punch

(Figure 20–10).

• Once firmly inserted, ¼“ tubing can be pushed

over the open end of the connector and run to

the fixtures on that line. Pushing tubing over the

barbed end connects emitters.

line and emitters are laid out correctly, use small wire

stakes to hold the line in place and cover the tubing with

mulch. Flag emitters will need to be adjusted to achieve

the desired flow rate, and micro-sprays will need to be

adjusted to aim the spray in the proper direction.

PREREQUISITE EXERCISES

Students should have successfully completed Exercise 1,

Construction Math, and Exercise 5, Tool Operation and

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86 Exercise 20 Irrigation System Installation

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Exercise 20 Irrigation System Installation 87

• Plumbing thread tape

• Drip irrigation system hose bibb connector

• Drip system pressure regulator

• Two spray emitters

• 20 wire anchors

• Tubing cutters

Cap

Barbed

connectors typ.

Compression

tubing

adaptor

Timer

Pressure

regulator

preventer

Hose bibb

/2“

90° Elbow

/4“1

/4“

6-16 Gal/Hr Inline emitters

Crimp ends

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