How to Install a Sprinkler System

With the turn of a knob, an underground sprinkler system can efficiently and evenly water your lawn. It’s not a project for inexperienced DIYers, but installing a sprinkler system is something a handy homeowner can do to keep the lawn looking its best.

Do Some Homework

Before you begin learning how to install a sprinkler system, you should start the project by doing your homework. Check your local municipality’s building and water codes to see if there are any restrictions on lawn sprinkler systems. You also need to know where any underground pipes or water mains might be located on your property. Your town’s Department of Public Works can help you.

You also need to know your home’s water flow rate in gallons per minute (GPM). Turn your outside faucet at full force and time how many seconds it takes to fill a one gallon container. Divide 60 by the number of seconds. This is your home’s water flow rate.

Next, look into the equipment you’ll use for your sprinkler system design. There are several different types of pop-up sprinkler heads that can be used in underground lawn sprinkler systems. Sprinkler heads used for trees, shrubs or lawns all differ in the type of spray pattern they produce. Depending on the type, a sprinkler head may produce a fine spray or a steady stream. It’s recommended you use only one type of head for the whole system, so if you want to water your lawn, you should use all lawn heads.

Plan out your sprinkler system design and draw it out on graph paper. Be sure there is proper overlap of the each sprinkler head’s spray so you’re watering your grass evenly. Your local True Value store expert can help you figure out which sprinkler heads are appropriate based on the size of your yard and your home’s water flow rate. They can also help you determine how much pipe and how many connectors, elbows and T-fittings you’ll need.

Installing a Sprinkler System

Step 1: Check for Proper Valves and Drains

Step one in learning how to install a sprinkler system requires you to check for proper stop valves and drains. Inside your house, find the location where the water pipe leads from the meter to the outside faucet. There should be a stop valve on this line. This stop valve will separate the sprinkler system water from the house water. This will come in handy, especially in winter. You can turn off the water to the sprinkler system so that you can drain it when you need to. There should also be a drain attached to this line.

Step 2: Attach T-Fitting

After completing step one, turn off the water at the stop valve on the line to the outside. Detach the outside faucet by unscrewing it with a wrench. Screw on an iron T-fitting so one projection points straight out and the other points straight down. Put the close nipple into the straight-out projection and re-attach the faucet.

Step 3: Attach Anti-Siphoning Valve

You should use PVC pipe to attach the anti-siphoning valve. The diameter of the pipe is determined by your sprinkler system flow rate: use 3/4″ pipe for 14 GPM, 1″ for 25 GPM, or 1 1/4″ for 40 GPM. If you have a different GPM, ask your local True Value expert what diameter pipe you need. Use the same diameter for the valves and fittings that you did for the pipe.

To attach any plastic-to-plastic (such as fittings, adapters, T-fittings or elbows), use plastic solvent glue. First prepare the plastic then test fit the pipe and the other piece. Mark the pipe and the other piece with a felt-tip pen so that you have alignment lines (the lines on each piece should line up). Also, mark along the edge so you know the depth of the socket that the pipe fits into. Use an emery cloth and clean the end of the pipe and the inside socket on the other piece. Prime the end of the pipe up to the alignment line and the socket with plastic primer.

Now apply a coat of solvent to the outside of the pipe and a coat to the inside of the socket. Do this quickly – the solvent dries in 30 seconds. Position the pipe so that the alignment lines are about 2″ apart. Shove the pipe in until it hits the back of the socket, then turn the pipe until the marks align. Hold for about 20 seconds, and then wipe off any excess glue with a rag (turning the pipe causes a solid bead of solvent to form around the pipe). Wait about two minutes before you handle it again.

Use a hacksaw or tubing cutter to cut pipe. If you have a hacksaw, just remember you have to support the pipe in a portable gripping bench or a vise because cutting straight can be difficult with a hacksaw. A tubing cutter is easier to use and can make a more controlled, precise cut. It is a good investment, especially if you are going to do more plumbing projects.

Cut two small pieces of pipe (the length depends on how high up the outside pipe is). Remember to take off the burrs with a utility knife. Attach a male adapter to one end of each pipe. Put Teflon® plumber’s tape on the threads of the adapters. Screw one of the pipes into the down projection on the T-fitting. Attach the other short piece to the pipe. Now screw it into the T-fitting with an elbow joint (the elbow joint can point to the right or left). Attach the anti-siphoning valve onto the other male adapter.

Step 4: Install Gate Valve

Cut another small piece of pipe and attach male adapters on both ends. Put plumber’s tape on the threads of the adapters. One end of the pipe goes into the anti-siphoning valve and the gate valve attaches to the other end of the pipe.

Step 5: Shovel Out Trenches

Successful lawn sprinkler systems need to reach every inch of your yard through underground trenches. Cut your trenches, starting where the pipe comes down the side of your home’s wall. The starting point of the trench needs to be 9″ deep and as wide as the head of your shovel. The trench needs to get 1/4″ deeper after every 5′ you dig. Continue with the slope wherever you branch. This slope allows the pipes to drain. Put plastic runners on both sides of the trench to avoid damage to your lawn. Use one runner for the sod and the other runner for the dirt. When the trench is done, line it with 1″ of gravel. This will also help the water drain. Mark where each sprinkler head will go by driving a stake into the ground.

Helpful Tip

Water the ground a few days before you dig. This softens the dirt and makes the whole job easier.

Step 6: Link Gate Valve to Pipe-run

Measure the length of pipe needed to reach from the end of the gate valve to the bottom of the trench. Take into account that there is a male adapter at one end and an elbow at the other. Attach the adapter with plumber’s tape on the threads and elbow. Dig out the gravel under the pipe so that you can attach the pipe to the gate valve. After attaching the pipe and adapter, scrape the gravel back around the pipe elbow. This elbow connects to the beginning of your pipe-run.

Step 7: Install Pipe-run

Measure, cut and connect the pipe to make your pipe-runs, laying it in the trenches as you go. Use elbows to turn corners and T-fittings to make branches. There needs to be a T-fitting wherever you put a sprinkler head. Also, one of the projections of the T-fitting needs to be up. Place the automatic drain valves into position at the end of the run and branches. Use male adapters to attach them with plumber’s tape on the threads. The automatic drain valves empty the water whenever the system is turned off.

Step 8: Attach Sprinkler Heads

The final step to installing a sprinkler system includes attaching the sprinkler heads. Cut the sprinkler head risers so the heads of the sprinklers are flush with the ground. Before making the cut, take into account the socket depth of the T-fitting and the male adapter that you have to add to the riser’s height. Using solvent glue, attach the adapter to one end of the riser. Add plumber’s tape to the threads. When dry, attach the riser to the T-fitting. To support the riser, embed a stake next to the head. Attach it to the riser using a block and wire then attach the sprinkler head.

Allow 24 hours for all pipe solvent to dry before testing the system. It may take a minute to flush out the pipe joints. If there are any leaks, fill the holes or cracks with plastic solvent cement and wrap it with plastic electrical tape. When the entire system works, fill in the trenches with the dirt and sod over them.

Helpful Tip

In the winter, turn off the water with the stop valve inside the house. Open the inside drain and place a bucket under it. Outside, turn the hose faucet and the gate valve for the sprinkler system on. This should get rid of water that is left in the pipes and prevent any damage from frozen pipes. The automatic drain valves open to let out the water whenever the sprinkler system is turned off.

Congratulations, you’ve successfully learned how to install a sprinkler system! Put your new underground sprinkler system to work and watch your lawn grow.

Project Shopping List

Here’s what you’ll need to complete this project successfully.