SPRINKLER IRRIGATION SYSTEM DESIGN
This guide is a general approach on how to design and install a home landscape irri-gation system. The steps would be much the same for most any irrigation system:
1. Gather information.
2. Design the layout.
3. Select the materials.
4. Install the system.
Step 1: Gather Information
Decide whether you want a manual or auto-matic system. The process would be the same, except that a controller, automatic valves and wire are necessary to operate an automati-cally control-led system.
We recommend if it is a large or complex system, you should get the help of a Certified Irrigation Designer or a qualified landscape architect.
Find Out The Following Information:
a. Static water pressure _________ psi
If you have city water call your local water department or use pressure gauge on garden valve output nearest area to be watered—no water should be running in or around the house.
b. Water meter size
Check meter or call local water department.
c. Gallons per minute Use chart below if you have city water or if you have a pump use the following: Run hose bib until pump turns on, then measure gallons per minute (the time it takes to fill a 5 gal. or other known quantity bucket) and note pressure on pressure gauge on the side of the pressure tank. Use the following formula to determine gallons per minute (GPM): divide the container size (in gallons) by the seconds it takes to fill the container and multiply by 60. Example: if it takes 30 seconds to fill a 5 gal. bucket, you have 10 GPM available.
| DETERMINING GALONS PER MINUTE (GPM) | ||||||||||||
| SIZE OF | STATIC WATER PRESSURE (PSI) | |||||||||||
| WATER METER | SERVICE LINE | 30 | 35 | 40 | 45 | 50 | 55 | 60 | 65 | 70 | 75 | |
| GALLONS PER MINUTE (GPM) | ||||||||||||
| 5/8” | 1/2″ | 2.0 | 3.5 | 5.0 | 6.0 | 6.5 | 7.0 | 7.5 | 8.0 | 9.0 | ||
| 5/8” | 3/4” | 3.5 | 5.0 | 7.0 | 8.5 | 9.5 | 10.0 | 11.0 | 11.5 | 13.0 | ||
| 3/4” | 3/4” | 6.0 | 7.5 | 9.0 | 10.0 | 12.0 | 13.0 | 14.0 | 15.0 | 16.0 | 17.5 | |
| 3/4” | 1” | 7.5 | 10.0 | 11.5 | 13.5 | 15.0 | 16.0 | 17.5 | 18.5 | 20.0 | 21.0 | |
| 3/4” | 1 ¼” | 10.0 | 12.0 | 13.0 | 15.0 | 17.0 | 18.0 | 19.0 | 21.0 | 23.0 | 24.5 | |
| 1” | 3/4” | 6.0 | 7.5 | 9.0 | 10.0 | 12.0 | 13.0 | 14.0 | 15.0 | 16.0 | 17.5 | |
| 1” | 1” | 10.0 | 12.0 | 13.5 | 17.0 | 19.5 | 22.0 | 23.5 | 25.0 | 26.0 | 28.0 | |
| 1” | 1 ¼” | 12.0 | 15.5 | 17.5 | 21.0 | 23.5 | 26.0 | 28.5 | 30.5 | 32.5 | 34.0 | |
| (subtract 5 GPM for galvanized pipe) | ||||||||||||
d. Plumbing regulations, building permits needed. Call city hall or your local building department.
e. Inside diameter of pipe (service line) running from water meter or pump to house. Wrap a piece of string around the outside of the service line. Measure the length of string required to encircle it. Look up service line size from following chart.
f. Determine backflow prevention device requirements of city or water system. A cross connection creates the possibility of back siphonage or contamination of potable water, and a backflow preventer is a must. High hazard conditions exist where a fertilizer injector is installed.
| FINDING PIPE DIAMETER USING A STRING | ||||||
| LENGTH OF STRING WRAPPED AROUND THE PIPE | 2-3/4” | 3-1/4” | 3-1/2″ | 4-0″ | 4-3/8” | 5-0” |
| Size of Copper | 3/4″ | 1” | 1-1/4” | |||
| Size of Galvanized | 3/4″ | 1” | 1-1/4” | |||
Step 2: Plan Your System
Use a Planning Grid to Make an Accurate Scale Layout of Your Property.
a. Include location of house, driveways, walkways, paths, fences, walls, structures, planters, patios, flower beds, shrubbery and lawn areas (see diagram 1)
b. Shade in all area to be covered by water: lawns, shrubbery, special grounds, etc.
c. Indicate water supply locations: spigots, well, water service entrance, etc.
Step 3: Select & Position Sprinkler Heads.
STEP THREE: Select and position your sprinkler heads.
a. See Product Guide. It identifies the major types of standard heads, gives their uses and gallons per minute (GPM), tells what patterns are available, and suggests correct spacing requirements. This is a general chart. For more specific information, check the manufacturer’s performance charts.
Step 4: Determine Size, Number, Type, & Location of Valves
b. Begin graphing large lawn areas. Place quarter circle heads in the corners. Place half circle heads between corners, following recommended equal distant spacings (refer to Product Guide). Place full circle heads within each perimeter, the number will depend on the perimeter’s overall dimensions. Study Diagram 2, a typical yard area showing positioned sprinklers. Impulse pop-up spinklers may be used if area size permits (refer to Product Guide).
c. Now position heads in small lawn areas, parkways, and at the side of your house. These areas are usually watered by one or two rows of part circle heads.
See Diagram 3.
d. Complete graphing of heads by positioning them in flower beds, shrubbery areas, planters and other special places. See Diagram 4. Shrub head patterns are equivalent to regular head patterns. For good coverage you want to have 100% overlap of heads.
e. Irrigation heads and bubblers should be used in tree wells, planters, for ground cover, and around plants that require soaking.
Step 5: Determine Size of Supply Line
a. The supply line is the piping from your water source such as your water meter or well, the line servicing the dwelling, or the existing outlet shown in Diagram 10- to the sprinkler valves.
b. Because of friction loss in the supply line, it is necessary to consider the distance from the connection to the valve location. If the tie-in point to your water meter, service line, or existing outlet is within 50 feet of the valve locations, use a supply line pipe equal to the size of your largest control valve. If between 50 and 100 feet, use one size larger than your largest control valve. If an existing outlet is being used, it must be as large as your control valve. The situation may arise where your supply line is larger than your control valve. In this case, it is necessary to reduce the supply line reducers to the size of the valve.
c. Determine the type of pipe you wish to use. It is recommended that PVC Schedule 40 be used to supply valves and then PVC Class 200 or poly-pipe after the valves, for residential systems. PVC is semi-rigid and comes in 20’ lengths with glue type joints. Poly-pipe is a flexible hose type pipe and comes in 100’ or larger coils. This pipe is attached
with insert fittings rather than glued joints. Poly-pipe is somewhat less susceptible to freeze damage. Warning: do not use poly-pipe as the connecting pipe between the service line and control valves. Surge pressure may rupture poly-pipe.
d. Once the pipe is selected, draw lines on the plot plan connecting the sprinklers in each zone to eachzone valve. The gallons per minute (GPM) used by any zone may not exceed the total capacity of your home’s water system. If it does, the circuit will not operate properly. Use the following chart to size the pipe lines you have drawn in, using the total GPM for each zone.
MAXIMUM FLOW IN GALLONS PER MINUTE
PIPE SIZE PVC Class 200 PVC Schedule 40 and Poly-pipe
1/2″ 6 4
3/4″ 12 8
1″ 18 13
Step 6: Group Sprinklers & Graph Plan
STEP SIX: Group your sprinklers and graph your piping plan.
a. A sprinkler group is the number of sprinkler heads adjacent to each other that will work off of the same control valve. If at all possible, all sprinklers in a group should be of the same function. For example, only bubblers should be grouped together. Start at the end of each particular sprinkler group and work towards its control valve, noting the number of planned heads. If you have three valves you will have three groups of sprinklers. See Diagram 7.
b. Determine the number of circuits needed. Maximum Flow chart above shows the maximum GPM flow that may be drawn by a circuit and still assure proper operation. This flow rate depends on 3 factors: the service line size, the static water pressure, and the type of sprinkler used. Refer to the information you gathered earlier and use the Maximum Flow chart to determine the GPM available for the operation of one circuit.
c. Start at the control valve and layout the piping system. Draw a feed line through the middle of each sprinkler group. Draw in side branches to adjacent heads. See Diagram 8 for a typical piping layout.
Example: Determining Gallons/Minute chart indicates that with a 3/4” supply line and 40 psi, you have 9 gpm available.
Step 7: Set The Controls
Product Guide indicates that each full circle (360°) spray head uses 3 gpm. If you divide the 3 gpm into the 9 gpm (9 divided by 3=3), or 3 full circle spray heads on each valve. If you use all half circle sprays, you use 6 sprinklers (9 divided by 1.5 = 6).
Lay out the piping.
In your system piping will run from the service line (source of water) to the first set of valves, then from the first set of valves to the second set, etc., and from the valves to the sprinkler heads.
Draw in these connecting pipes on your grid layout and follow these rules:
1. Use as many straight runs as possible.
2. Avoid turns which result in friction and loss of pressure.
3. Avoid going under sidewalks and driveways whenever possible.
To avoid forcing water through too many turns (right), design connecting pipe so that several lines branch from the first head in the circuit (left) (Diagram 9).
Review your plan, then order what you need.
a.Check over the details of your plan carefully, then order selected sprinkler heads and valves from Harmony Farm Supply.
Step 8: Set Your Control Valves.
Setting your control valves.
a.To connect the supply line, shut off water at the meter, cut a section of the service line and insert a
standard slip coupling tee. Run the supply line to the location of your valves. See Diagram 10. To
connect to an existing garden hose outlet, simply remove the valve and insert a nipple and a tee.
Replace the hose valve and run pipe down to the sprinkler valves. See Diagram 11.
DIAGRAM 10
b.A group of valves is called a manifold. Diagram 12 shows an example of a manifold for three valves.
In a manifold, use fittings and pipe the same size as your valves. If more valves are needed, additional
fittings would be added. Always install a master shutoff valve before your control valve manifold.
c.Install your valves, making certain that anti-siphon valves are 6” above the ground and 5”
apart to allow for an adapter to automate the system at a later date. Angle valves should be
buried. Refer again to Diagram 5 for typical valve installations for a single valve or refer to manifold
valve hookup.
d.Do not install anti-siphon valves under constant pressure.
Step 9: Position Sprinkler Heads
Positioning your sprinkler heads.
a.Using stakes (or sprinklers) and string (for piping), mark the locations of your heads and piping. See
Diagram 13. Important-Maximum GPM flow may vary significantly because of pressure losses result-
ing from size and type of pipe used as well as the total length of pipe in an installation. Another
important factor is elevation, because you will lose approximately 1/2 psi per foot of elevation going
up a hill, and gain approximately 1/2 psi per foot of elevation going down a hill. Therefore, before
backfilling any trenches, hook up each circuit and test for sufficent coverage.
b.Dig trenches 5” to 6” deep, putting any sod on one side and any dirt or soil on the other side of the
trench. For cold climates, lay the pipe so the water will flow to a drain valve which should be installed
at the lowest point. Hard ground should be watered two days before trenching.
Trenching machines are an easier, faster alternative to digging with a spade (see Diagram 14). They can
be rented by the hour, day or week-usually from a lawn-supply store or rental equipment dealer. The
person you rent from can show you how to operate the machine properly and safely. Trenchers should
not be used to dig through ground cover, flower beds, on steep slopes or near buildings.
Going under obstacles—a hose may be used to tunnel under brick and concrete walks (Diagram 15).
Attach a piece of galvanized pipe to your hose with a hose-to-pipe adapter. Point the end of the pipe
where you want to tunnel. Then turn on the water. Push the pipe under the concrete; the force of the
water will blast away soil to form a tunnel. Tunneling requires care to avoid damage to walks and driveways.
c.Locate valves. Valves can be located above ground or, to keep them out of sight, below ground. Use
stakes to mark the locations of the valves as indicated on your grid diagram.
Protect valves by sheltering them in boxes. You can buy boxes or build them yourself. If you buy boxes,
check to see how many valves each box holds. If you build the boxes, we recommend using high-
quality redwood because it resists rot.
d.After hooking up, close all the control valves on your manifold and open the master valve. Check
all connections for leaks.
Step 10: Connect Piping
Connecting your piping.
a.After all trenching is finished, connect all threaded fittings first, starting at the water source. Then con-
nect all slip or insert fittings. If using galvanized pipe, use an adequate amount of pipe joint com-
pound; if using plastic pipe, be certain of a leak-proof seal. See Diagram 16.
b.How to cut and connect PVC pipe:
1. Cut PVC pipe to desired length with a hacksaw or PVC cutter. Wipe cut clean and remove burrs.
2. Apply solvent and glue to both pipe and fitting.
3. Push pipe as far as possible into fittings. Make 1/2 turn for sure sealing.
4. Wipe off excess solvent and glue.
c.Locate valves. Valves can be located above ground or, to keep them out of sight, below ground. Use
stakes to mark the locations of the valves as indicated on your grid diagram.
Protect valves by sheltering them in boxes. You can buy boxes or build them yourself. If you buy boxes,
check to see how many valves each box holds. If you build the boxes, we recommend using high-
quality redwood because it resists rot.
d.After hooking up, close all the control valves on your manifold and open the master valve. Check
all connections for leaks.
Step 11: Flush System
a.Flush the main line. Wait for the solvent to dry (about one hour). Close all valves except the one at
the end of the line. Turn on the water. Flush until the water runs clear. Shut off the last valve and
check for leaks.
b.Flush the valves. This removes any dirt or soil that may have gotten trapped in the valves during
installation. Open the valves using manual bleed finger screws or knobs. Turn on the water and flush
valves until the water runs clear. Check for leaks and proper operation.
c.Install the automatic system timer. Locate the timer in your garage or some other convenient
place. Make sure an adequate power supply is available. Timers require only a standard AC outlet.
Run wires along the trench from the valves to the system timer. Take one wire from each valve and
connect to a common terminal on the timer. Take the other wire from each valve and connect one
wire per terminal to the other terminals in sequence. See the instruction sheet that comes with
your system timer for full details. Plug in the timer. Test the system by electronically opening and clos-
ing each valve in sequence. When the controller has been installed and fully tested, fill in the trench
with dirt; then replace the sod.
d.Flush the system. Seal risers with pipe plugs. Leave the riser at the end of the line unplugged. Turn on
the water, open the valves, and flush until the water runs clear. Remove the pipe plugs.
e.Install sprinkler heads. Attach sprinkler heads to risers. Check your grid diagram to make sure you
attach the right head to each riser. Check the height of the heads. If necessary, cut risers to adjust head
height. The top of the sprinkler should be flush with ground level (see Diagram 17). Re-install the
sprinkler heads.
Step 12: Check System Operation
Turn on the water and open the control valve. If coverage is incomplete:
1.Make sure the control valve, main valve and shut-off valve are open all the way.
2.Turn off any water being used in the house (washers, showers, sinks).
3.Adjust the screws on the sprinkler heads to fine-tune the spray pattern.
4.If coverage is still not complete, go back and check your system layout against the plans.
5.When coverage is satisfactory, fill in the trench with dirt and cover with sod.
6.You’ve just installed a working circuit. To finish the job, repeat these steps for all circuits in the system. Relax and install the system one circuit at a time.
HINTS ON OPERATING YOUR SYSTEM
1.Operate only one valve at a time.
2.Water when pressure will be the greatest. This will probably be early in the morning.
3.Water shrubs, trees and plants deep and less frequently.
4.Water lawn areas for shorter periods and more frequently.
5.Do not water in the heat of the day to cut down on water evaporation. This will also eliminate the burning of plant and lawn areas.
6.Sprinklers should be cleaned periodically to insure proper functioning.
We thank Champion Brass Manufacturing Company, Buckner-Royal Coach Sprinklers, Inc. and Toro Irrigation Inc. for the permission to use parts of their planning guides.