A sprinkler system adds significant value to a residential property and can save a yard-care person time and money. However, a professionally installed system normally costs from $1500 to $2500 for a 2500 ft2 front lawn. An average or $2000 system usually breaks down as follows:
- plumbing connection $500
- electronic controller $300
- piping and heads $500
- labor $700
Adding a 2500 ft2 back yard tacks on another $1000.1 I was able to install a basic but effective system on my own for just over $500.2 A year later it still runs smoothly and I continue to realize the benefits of my labor. The secret? I use the unique method of installation3 detailed herein featuring flexible PVC, long-range rotors, in-line timers and filtered drains. This article details that installation process, but it is assumed that the installer has taken all necessary preliminary action (e.g., investigating if a sprinkler system would be advantageous and effective in the desired location,4 any and all legally required action,5 etc.).
While planning is the most time consuming part of putting in a sprinkler system, doing it well can save you significant work and ensure effective watering. The following planning steps are intentionally brief as detailed planning6 is outside the scope of this article. The fundamentals, however, are all present.
Plot Your Lot
Start planning your sprinkler system well in advance of the planned installation date as this will keep you from sacrificing quality to meet a deadline. Begin by obtaining a lot survey which should be among the appraisal information you received when you bought your home. If you are unable to obtain a survey of the lot you will have to measure its dimensions manually. Plot the gathered information using a graphing computer program (the most effective and exact method) or a pencil and a sheet of graph paper. If you go the paper route, be sure to sketch the lot large enough; a smaller plot is less exact and harder to work with. Once the general geometry of the yard, home, driveway, sidewalks, fences and other important features are plotted, mark the locations of all available water spigots.
Additional Preliminary Information
Depending on the extent of your planning process, you may need to gather the following information before continuing.
- Water pressure – Determine your water pressure either manually through the use of a pressure gauge or by calling your local municipality. If using the pressure gauge, turn off all other water faucets (both inside and out) and attach the pressure gauge to an outside faucet. Turn the water on at the appropriate spigot and record the pressure reading7 on the gauge.
- Water meter size – Determine your water meter size from either the meter itself, a utility bill, or your water provider. Water meters are typically 5/8", 3/4", or 1".
- Service line size – Determine your water service line size by wrapping a piece of string around your water service pipe once and then measuring the length. Compare the result to Table 1.
- Flow rate – Determine your water flow rate by timing how long it takes to fill a container to a measurable level. Divide the filled volume by the measured time and convert to gallons per minute or gallons per hour.8
The sprinkler heads you choose determine the rest of your design and they are a key component to this unique installation. Opposed to most residential systems that include many stationary, small sprinkler heads in a grid covering the lawn, this method involves using fewer, larger, rotor-style heads which will require less installation materials and labor. The most popular sprinkler system brands are Rain Bird and Orbit, both of which offer rotor-style heads to meet this need. Styles with adjustable ranges are particularly convenient, as a home’s individual water pressure and flow rate will cause head performance to vary greatly. In this installation, I use the Rain Bird 32SA Full and Part Circle Gear-driven Rotor.
Once you have selected sprinkler heads, toy with various arrangements on your yard plot. Irrigation system design sites all encourage head to head coverage,9 but I recommend starting with single coverage and then expanding later as required. Look to minimize the number of heads necessary by adjusting placement. You may even choose, as I do, to neglect certain areas of the yard that either need less water (e.g., areas watered by drainage or the neighbor’s sprinklers, shaded areas, less needy plant/grass types, etc.) or that you are willing to let die. The two neglected areas in my yard plot are the thin strip of grass along the right side of the house (shaded and gets runoff from both my and my neighbor’s backyards) and the thick segment on the left-front (neglected due to location).
Try to avoid placing heads between the sidewalk and the street (if applicable) as they are harder to install. Place as many heads as possible close to fences or walls as heads in low-traffic areas are less likely to get damaged. I forego this last piece of advice in my initial plan, as evident by the heads in the backyard noticeably located away from fences and walls, with the intention of keeping the number of heads to a minimum (see Adding and Adjusting the System).
After deciding on a head placement, divide the heads into zones. Your water pressure, flow rate, and head size will determine how many heads you can put on one zone. My final design included six sprinkler heads so I assigned two to each spigot. Plot lines from each spigot to the heads for which they will provide water. Straight lines are not necessary (more on that later) but, again, avoid running lines under sidewalks or driveways if possible. After the head locations are secured, it may help to measure distances on the plot from landmarks (e.g., fences, sidewalks, walls, etc.) to facilitate locating the corresponding spot in the yard.
After a nice and thorough planning stage, let the buying begin. Although the shopping list will vary, the following guidelines may prove helpful, as well as provide a preview to the system and how it will work. I suggest purchasing materials for only one zone initially and installing it as a test zone. This will also spread out your expenses and work load, as well as allow you to adjust your planning for other zones if necessary.
Splitters and Timers
To avoid having to pipe to a manifold and buy an expensive timing system, I use one relatively inexpensive in-line timer for each zone. These timers hook up directly to the spigot, are battery powered and weather-proof. I also purchase a splitter for each spigot to allow access to direct water without having to disconnect the sprinklers. Note, however, that neither a splitter nor timer is necessary for a functional sprinkler system; you may choose to postpone the purchase of one of both in order to spread out the cost. Integrating them at a later date is next to effortless.
Purchase the number of heads indicated by your planning, whether for your test zone or all zones. Be sure to save the head receipts, however, as heads are returned frequently. Not only are they the most defect and damage prone, they are often poorly chosen. With a receipt, damaged, defective or poorly chosen heads can be returned and replacements bought after any necessary planning adjustments.
The type of piping used is another key attribute of this installation method. Instead of the typical rigid PVC, I use 3/4" flex PVC. Flex PVC is more expensive and harder to find than rigid PVC, but it more than makes up for the purchase cost and inconvenience through the following advantages:
- Connection Frequency Reduction – Flexible PVC is easily bent and maneuvered and does not require connections at corners, angles, or changes in depth.
- Plan Flexibility – Because flex PVC can adapt to most any line configuration (other than very sharp turns that will kink it), you can change line direction easily, even in the middle of installation, without having to hassle with re-thinking the entire line design or purchasing additional connections.
- Backflow Prevention – The line flexibility allows a simple and inexpensive solution to prevent backflow through the line. (See Installation: Connection to the Spigot and Figure 24)
- Adaptability – The spigot hookup method allows things like fertilizer to be easily added to the yard through the sprinkler system.
- Cutting – Flex PVC can be cut and prepped easily with a utility knife whereas normal PVC requires additional tools and effort.
Normal, rigid PVC fittings can be used to make flex PVC connections. These are very inexpensive, so I suggest buying some spares to avoid an extra trip to the hardware store. Outside of basic unions (Figure 10) and tees (Figure 11), this sprinkler system installation will require some slightly specialized fittings:
- Soc 3/4" x Soc 3/4" x 1/2" female NPT10 – This connection will go at the base of each sprinkler head. It is just like a 3/4" tee, but the intersecting opening is prepared for a 1/2" male NPT fitting. See Figure 12.
- 1/2" x 6" Riser11 – One of these is needed to connect the bottom of each sprinkler head to the tee below. 1/2" represents the size of the connection (1/2" male NPT) and 6" represents the length. Various lengths are available with segments that can be cut off to provide the proper head height. See Figure 13.
- Spigot to 3/4" Soc – One of these will be needed at each spigot. See Figure 14.
- 3/4" Soc to 1/2" female NPT – Most drains and plugs have a 1/2" male NPT thread. Thus, for each drain installed, an adapter will be needed going from 3/4" PVC to 1/2" NPT. See Figure 15.
The final key aspect of this installation method is the use of filtered drain valves. Filtered drains hold pressure during watering and allow water to seep out of the piping between uses. Without the potential for residual water in the lines over winter, you can bury the piping above the freeze line which greatly reduces the labor and machinery needed. Purchase at least one drain for each line to be installed at the lowest spot in the circuit. If there are multiple low spots, use more than one drain.
Tools and Other Materials
You will also need to gather the following to perform the installation:
- Shovel – A spade style shovel with a handle works best.
- Glue – Standard PVC cement will be used for the connections. Primer is not necessary and a 4oz can will suffice for most yards.
- Knife – You will need a box-cutter or utility knife to cut the flex PVC.
- Teflon Tape – You will need a roll of 1/2" Teflon tape for threaded connections (except where noted).
Figure 17. Teflon Tape .5″ × 260″ ($1.98 @ Lowe’s), PVC Cement ($3.35 @ Home Depot), Utility Knife ($3.96 @ Lowe’s), and Utility Knife Blades ($0.98 @ Lowe’s)
Once you gather all of the necessary materials, the installation fun can begin. The following instructions will detail the main installation steps. While it is important to start with Preparation and end with Covering the Lines, some of the steps can be interchanged.
Before grabbing the shovel and going nuts on the yard, you may want to either wait for some rain or water the area with your soon-to-be-obsolete manual sprinkler. Depending on the hardness of the ground, a little water could make the digging much easier. Also, string your flex PVC out on the driveway or porch so it can get some sun. This will soften the pipe and make it easier to cut and bend.
Instead of digging trenches you will be ‘slotting.’ To create slots, insert a spade-style shovel about six inches into the ground and pull back. Then flip the shovel and do the same thing in the opposite direction. Repeat this process all along the path of the future underground line. It may be helpful to test the size and depth of the slot by jamming a segment of flex PVC into it after a few feet have been slotted (there is no need to cut the PVC to accomplish this). Adjust your digging style per your findings.
Getting the lines into the slots is easy enough once you have slotted the way, but some planning is necessary before starting. Start at the spigot end of the slot and leave enough PVC to run up to the spigot, plus an additional three feet (which will be explained later). Then insert the flex PVC into the slot by jamming it in place with the handle of shovel or the head of a medium sledge hammer. At the other end of the line and at any sprinkler head location, cut the line leaving an extra three to six inches. Repeat the process for other lines to be installed, keeping in mind that it’s much easier to cut a few extra inches off than to add a connection to lengthen the line by the same distance. After putting the lines in the slots, all that remains is to bury them by pushing the sides of the slot back together. I recommend you postpone this step, however, until after the system has been tested to avoid having to dig up and re-bury lines if any adjustments are necessary.
Making Connections / Installing Tees
You will have to make multiple connections on each line. Follow the same procedure whether you are inserting a tee to split the line on the way to two different destinations, installing an in-line sprinkler head, or ending the line to add a plug or drain. See Video 1 for a video of making a connection.
- Cut the PVC – Use the utility knife. Avoid cutting at an angle; a flat surface will allow for the best connection.
- Clean and Dry – Make sure all pieces to be connected are dry and free of debris.
- Test the Connection – Test-join the pieces (prior to applying cement).
- Apply Cement – Swab around the outside of the male end and the inside of the female end.
- Make the Connection – Insert the male end into the female end and make a half turn to spread the glue evenly.12
- Drying – Allow sufficient drying time before applying pressure.13
Installing Sprinkler Heads
Most heads come with detailed installation instructions. Read these thoroughly, including information on adjusting the coverage of the head after its installation.
Follow the same installation process at each sprinkler head location. Start by wrapping Teflon tape around the 1/2" male NPT end of the riser prior to screwing it firmly into a 3/4" x 1/2" female NPT tee. If the riser has multiple segments, you can now cut it to fit whatever depth you wish to bury your line. I recommend cutting off all but one full threaded segment using the utility knife. This will save you some digging trouble by allowing you to bury the line as shallow as possible. Next firmly screw the sprinkler head onto the riser and then back it off one full turn. This combination of the tee, riser and sprinkler head will be referred to as the head assembly.
Next, make an extra-wide and deep slot at the future sprinkler head location to accommodate the sprinkler head assembly. Just how ‘extra’ will depend on the size of your sprinkler heads and how deeply you are burying your line. The slot is sufficient when it is deep enough to keep the top of the head assembly at dirt level and wide enough to allow the sprinkler head to be turned by hand.
Once the slot is done, place the head assembly in the slot and position it as if it were installed (with the through tee turned to be in-line with the PVC). Run the PVC through the slot up to the head assembly to approximate where to cut. Cut the PVC and connect it to the head assembly per the instructions in the ‘Making a Connection’ section, making sure to test the head position when testing the connection without cement.
Most lines terminate at a sprinkler head location.14 However, instead of plugging the end of the head assembly base tee, install a six to twelve inch segment of PVC and then a 3/4" Soc to 1/2" female NPT fitting. Then, wrap a layer of Teflon tape around the threads of a plug or drain and screw it firmly into the fitting. The extra segment of PVC will allow you to connect in future lines or replace/move the drain without having to disassemble the head assembly.
Connecting to the Spigot
At the spigot end of the line, install a splitter, timer and 3/4" Soc x Spigot fitting. Close all valves on the splitter and spigot, apply a layer of Teflon tape to the spigot threads, and tightly screw on the splitter. Turn on the spigot faucet to check the integrity of the connection. If there are no leaks, then apply a later of Teflon tape to the timer threads and tightly screw on the timer.15 Ensure the dial on the timer is in the "OFF" position and then open the splitter valve on the branch leading to the timer to check the integrity of that seal.
Before connecting the line to the timer, configure a make-shift backflow-preventor by burying a loop made of the extra PVC mentioned previously. Make the loop as small as possible to avoid extra digging, but be sure not to kink it as this will restrict water flow. This loop will provide a high spot in the line which will prevent backflow of dirty yard water into the house’s drinking water supply. Alternatively, a backflow prevention device or vacuum breaker16 can be purchased and attached to the line.
With the loop and timer in their desired final position, cut the PVC to length against the spigot. Although the timer and splitter will most likely account for some of this distance, leave enough length to connect to the spigot directly.17 Glue the PVC into the 3/4" Soc x Spigot fitting and, when dry, connect to the timer threads using Teflon tape.
Testing the System
Once you have slotted, run the lines, installed the head assemblies and terminated the lines, it is time for a system test. This can be done before any of the lines or heads are buried to allow you to make any needed changes. Turn the timer dial to "ON" and inspect the performance and integrity of the system. The heads will most likely not be shooting the proper distance or direction as you have not yet adjusted them and they do not have the support of the ground around them. The important thing to check for first, however, is if the system is holding pressure and if the pressure is sufficient to function all of the heads. If the water does not pop up the sprinkler head rotors or if the water shoots a very short distance, you either have a leak or you over-estimated your water pressure. In many cases, the water pressure is more than sufficient, shooting the water into the neighbor’s yard or over fences. This is the optimal case; you can adjust the range of the heads and there is enough pressure to push additional heads if an expansion is added in the future. Check all connections for leaks and turn the timer dial to “OFF.:”
Adjusting the Heads
Most turning sprinkler heads have a fixed left-stop that you must align with the left end of the coverage area. To find the left stop, rotate the head rotor with the palm of your hand all the way to the left, then all the way to the right, and then all the way back to the left. The ending position is the fixed left-stop.
After the left-stop is located, tighten the head onto the riser (without turning the rotor) until the left-stop is aligned with the left end of the coverage area. This tightening is possible because the head was backed off in Installing Sprinkler Heads. While tightening, pay attention to the difficulty of turning the head; tighten it enough to make a seal but not so far that the threads on the head or riser are compromised. When all of the heads on the system are aligned, turn the water on to observe the left-stop alignment. After making any necessary adjustments and burying the heads as described in Covering the Lines, you can make the remaining head adjustments: right-stop alignment and radius. Figure 23 shows the adjustment system of the Rainbird 32A head: a larger slotted screw (top) to adjust the turning angle and a smaller slotted screw (bottom) to adjust the coverage radius.
Covering the Lines
Close the slots over the top of the PVC lines by stomping on their sides. If you are a light-weight, you can use the handle of a shovel or the top of a sledgehammer. Watering the ground may also help. Before closing in the slot around the heads, be sure the top of the head sits low enough so as to be inconspicuous and avoid the lawnmower, but high enough not to become covered or overgrown. When it is at the correct depth, be sure to pack the sprinkler heads in firmly, avoiding head tilt as much as possible.
How Much and When to Water
Once your system is installed it is time to set the watering cycle. How long and how often to water depends on your grass type, soil type, weather and the rotation of your heads. A good rule of thumb to follow is one inch of water per week.18 An easy way to gauge how much your system waters is to measure how long it takes to fill a tuna can, being careful to note that coverage may vary from location to location. Alternatively, place four tuna cans in different locations and water for 15 minutes. Then, combine the contents of the cans into one can and measure the height. This is your approximate watering rate per hour. Also, it is usually best to water in the early morning hours. Water pressure is usually highest at this time and you can minimize the water lost to evaporation. The early morning is preferred over late at night to prevent fungus growth.19
Adding to and Adjusting the System
After observing your system’s performance and the subsequent grass growth, you may wish to expand or modify your system by adding or moving a head. An addition is easily accomplished by carefully digging up the nearest line, cutting it, adding a fitting and then plumbing the new head to it. Figure 24 shows a number of modifications I make to my system: an added line and head for more water in the front yard (purple),20 and a moved head to provide additional coverage next to the fence in the side yard (red). You can make as many modifications and additions as you want, as long as the water pressure is sufficient to run all the installed heads to the desired coverage.
Once the system is installed it requires very little maintenance. However, you should be aware of the following guidelines:
- Short-Term Disabling – Avoid over-watering at times of precipitation by following the timer’s instructions for temporary disability. If you are using the timer pictured in Figure 7 and Figure 21, this is accomplished by simply turning the dial to "OFF." When watering is again needed, turn the dial back to the previous watering duration and the timer will revert back to the previous watering cycle. Alternatively, the timer can be left alone and the faucet turned off. The valve in the timer will still open and close, but no watering will occur.
- Long-Term Disabling – During winter, timers and splitters may be removed if desired.
- Adjustments – Adjust watering cycles according to the weather. Heat, drought and rain may all warrant watering changes.
The Finished Product
When completely finished, take time to enjoy watching your system in action. Also, consider giving your old manual sprinkler a proper goodbye with a sledgehammer or a 100 ft drop, whichever brings you more satisfaction. Alternatively, you may choose to wire it to the grill of your car or truck as an everpresent reminder, or simply to enjoy a good chuckle while pawning it off on some poor, sprinkler-moving sap. In fact, you may find yourself enjoying such humor often – anytime you see a a professional installer backing a trench digger off of a trailer, observe a neighbor’s watering ritual every half-hour, or happen upon an overturned traveling tractor-sprinkler pathetically digging itself a muddy grave. Chuckle on, my friend; you have conquered.
1 Foster, Ruth S. “Choosing a Sprinkler System for Your Lawn.” BobVila.com. Accessed July 2005 from http://www.bobvila.com/ArticleLibrary/Task/Landscaping/SprinklerSystems.html.
2 Examples of very detailed but unnecessarily complicated installation guides: Barnhart, Roy. “How to Install an Underground Sprinkler System.” DoItYourself.com. Accessed July 2005 from http://doityourself.com/lawn/installundergroundsprinkler.htm. Stryker, Jess. “Landscape Sprinkler and Drip Irrigation Installation Tutorial.” IrrigationTutorials.com. Accessed July 2005 from http://www.irrigationtutorials.com/install.htm.
3 The method of sprinkler system installation described herein was developed and taught to the author by Eric Larson.
4 According to “Installing an Underground Sprinkler System” on Lowes.com(Accessed July 2005 from http://www.lowes.com/lowes/lkn?action=howTo&p=LawnGarden/UndergroundSprinkler.html&rn=RightNavFiles/rightNavHowTo): "Some areas do not adapt well to portable hose end sprinklers. Under some conditions, a high arcing spray emitted from a sprinkler may blow away or partially evaporate before it hits the ground. The type of grass in your lawn also determines irrigation needs. Some turfgrass varieties have higher water requirements than others."
5 Required legal action may include doing the following: Determine if your locality requires a building permit. Check for underground utilities before digging by calling the North America One Call Referral Service at 1-888-258-0808. Research your local municipal watering ordinances. Check your local building codes to identify any potential issues.
6 Some useful sites for further information on planning: “Installing an Underground Sprinkler System.” Lowes.com. Accessed July 2005 from http://www.lowes.com/lowes/lkn?action=howTo&p=LawnGarden/UndergroundSprinkler.html&rn=RightN&avFiles/rightNavHowTo. “Sprinkler Design Service.” Rainbird.com. Accessed July 2005 from http://www.rainbird.com/diy/design/. “System Design Service and Guides.” Toro.com. Accessed July 2005 from http://www.toro.com/sprinklers/guides.html.
7 Pressure gauges typically provide pressure readings in units of pounds per square inch (psi).
9 Head to head coverage is defined as the end of one sprinkler range landing at the adjacent sprinkler heads.
10 NPT is an abbreviation for National Pipe Thread. National Pipe Threads are standard in the U.S. for tapered threads and are commonly used to join plumbing fittings.
11 A 3/4" Soc x 3/4" Soc x 3/4" female NPT tee may also be used. In this case, the riser should be configured to have a 3/4" NPT on bottom and 1/2" NPT segments on top.
12 Reference the instructions on the outside of the cement container to supplement the instructions included here.
13 Reference the details on the cement containter label for approximate drying times as well as other precautions/procedures to follow.
14 You may wish to run extra PVC from the last sprinkler head on the line if you plan on expanding the system later and want to install the PVC now.
15 If a timer is not to be installed at this time, simply skip this step and treat the splitter end as the timer end when following the rest of the installation instructions. If neither a splitter nor a timer is to be used, treat the spigot itself as the timer connection.
16 For more information on backflow and backflow prevention: “The Johnson Corporation: Vacuum Breakers.” Joco.com. Accessed July 2005 from http://www.joco.com/products/vacuumbreakers.html. “Backflow Prevention.” Eweb.org_. Accessed July 2005 from [http://www.eweb.org/home/water_quality/backflow.htmquality/backflow.htm].
17 This extra length will allow the line to be hooked up to the spigot directly in case of the removal of the splitter and/or timer. It will also give some room to insert attachments into the line, if desired, for things like fertilizer.
18 For more info on how much to water your lawn: “How Much Should I Water?” AllAboutLawns.com. Accessed July 2005 from http://www.allaboutlawns.com/lawn-maintenance-care/how-much-should-i-water.php.
20 While the area covered by the added sprinkler head appears from the diagram to already be receiving water, the need for more coverage here was apparant in the grass growth and color.
21 Yard diagrams were contructed using this software: “Autodesk Inventor.” Autodesk.com. Accessed July 2005 from http://usa.autodesk.com/adsk/servlet/index?siteID=123112&id=4291253.