An underground sprinkle can be a real time saver since it can be programmed with starting and ending times.  Moreover, watering your lawn, trees, plants, and shrubs on a regular basis will be easier than ever before.  Regular watering enhances the look of your yard and creates a pleasing effect.  Additionally, sprinkler systems provide even watering that leads to an even appearance of growth and color in your yard.

Initial Research Steps to Install an Underground Sprinkler System

  • Do a little local research and see if your township/county has any restrictions that relate to underground water systems.
  • Contact your local water department to locate any existing underground pipes.
  • Contact your local telephone, gas, and electrical department to locate any existing underground wiring or pipes.

Initial Preparation Steps to Install an Underground Sprinkler System

  • Determine the water pressure at your home.  Use a pressure gauge at an outdoor faucet.
  • Measure how much water your water system provides per minute, known as the flow rate.  Use a 1-gallon bucket or container placed underneath the same outdoor faucet.  Time how long it takes to fill the container.  Divide the resulting number of seconds by 60.  This will give you the flow rate in terms of gallons per minute or gpm.
  • Create a layout of your home and yard on graph paper.  Plan the positioning of your sprinkler system and add it to the drawing.  Be careful to allow the spray to overlap so that you can avoid any dry spots.
  • Use the information that you have gathered to help you determine the particular underground sprinkler system that you will select.  Different sizes of sprinkler heads have different outputs.  It is important to determine the proper size and number of sprinkler heads to purchase.  The larger sprinkler heads will have a higher flow rate, but they will also cover a larger area.

Since the sprinkler system should use approximately 60 to 75 % of your flow rate, you need to determine how much the combined total of flow rates for the sprinkler heads that you have selected will be.  If this number is higher than 60 to 75 % of your flow rate for your home, then you need to select smaller heads or fewer heads.  The employees at the sprinkler store should be able to help you with this calculation.

  • Next, you need to determine the size and type of pipes that you will purchase for your system.  The flow rate for your sprinkler system will determine the size of the pipe that you purchase.  A rough guideline is as follows: 1 ¼ inch for 40 gpm and 1 inch for 25 gpm.  Again, the employees at the sprinkler store should be able to help you with this calculation.

Select either PVC or CPVC, chlorinated PVC, pipe for your project.  Both types of pipe are easy to use since they are lightweight.  Moreover, they won’t corrode.

  • Check that your water system includes a shut off valve for the outside water.  If it does not, have one installed.  Additionally, check that your water system includes a drain so that you can drain the sprinkler system in the winter.  If it does not, have one installed.

Materials Needed for an Underground Sprinkler System

  • Graph paper and pencil
  • One gallon container
  • Shovel
  • Wrench
  • Utility knife
  • PVC or CPVC pipe
  • PVC or CPVC male adapters- 1 for each sprinkler head, 2 for each automatic drain valve, and 5 the underground pipe from the outside pipe
  • PVC or CPVC fittings
  • PVC or CPVC elbows
  • PVC or CPVC T-fittings
  • PVC or CPVC risers
  • Hacksaw or tubing cutter
  • Iron or steel T-fitting, threaded
  • Iron or steel close nipple
  • Anti-siphoning valve
  • Gate valve
  • Automatic drain valves (one for each branch and one for the end of the pipe run)
  • Gravel
  • New faucet if the old one will not fit
  • Sprinkler heads
  • Stake, wooden block and wire
  • Solvent glue and primer
  • Plastic solvent cement
  • Emery cloth
  • PTFE plumbers' tape
  • Plastic electrical tape
  • Felt tip pen

Steps to Install an Underground Sprinkler System: Working with the Existing Faucet

  • Cut the pipes to the proper length.
  • Turn the water to the outside off by using the shut off valve.
  • Take off the outside faucet using the wrench to unscrew it.
  • Place the iron T fitting on securely using the wrench.  It should have one opening pointing downward and another pointing straight out.
  • Place the iron close nipple into the opening that is pointing straight out.  Replace the faucet onto this end.

Hints to Follow When Working with the Plastic Pipes

  • Prepare the plastic for placement.  To do this, you need to test fit the pipe to the fitting, adapter, elbow, or T fitting.  Use a felt tip pen to mark the pieces at the proper juncture spots.
  • Use an emery cloth to clean the pieces.
  • Prime both of the pieces with the plastic primer.
  • Place a thick coating of plastic solvent to the outside of the pipe, but only a thin coating to the socket.  Remember that the solvent dries in approximately 30 seconds, so you will need to work quickly.
  • Position the pipe and the socket so that they are close together- about 2 inches.  Push the pipe into the socket until it is completely in, and turn the pieces to align the marks that you made.
  • Hold the pieces steady for the next 20 seconds.  Use a rag to wipe off any excess glue.  Use caution when handling because the solvent forms a line around the pipe due to the turning of it.  Wait at least 2 minutes before picking it up again.

Steps to Install an Underground Sprinkler System: Working with the Anti-Siphoning Valve

  • Measure the lengths of PVC or CPVC pipe that you will need for the outside pipe at the faucet and cut them.  At one end of the pipe, attach a male adapter.  Cover the threads of the adapter with PTFE plumber’s tape.
  • Using an elbow, attach the second piece of pipe to the one that you just placed into the T fitting.
  • Take the anti-siphoning valve and attach it to the other one of the male adapters.
  • Screw one of the pieces of your pipe into the iron T fitting’s opening that is pointing downward.

Steps to Install an Underground Sprinkler System: Working with the Gate Valve

  • Cut a small piece of pipe and attach one male adapter at each end.
  • Cover the threads of the adapters with PTFE plumber’s tape.
  • Attach one end of the pipe to the anti-siphoning valve.
  • Attach the other end to the gate valve.

Steps to Install an Underground Sprinkler System: Digging

  • Prepare the ground for the digging that is required.  Map out the area where you need to dig.  Lay a series of tarps or plastic runners to place the sod and dirt as you remove it.  This will help to protect the lawn next to your digging location as well as make the replacement of the dirt and sod easier to accomplish.
  • The trenches should be as wide as the shovel that you will be using.
  • The trenches should be 9 inches deep when you begin.  After every 5 feet, add another ¼ of an inch to the depth.  This will create a sloping effect for the pipes that will allow them to drain.
  • Every time that you change direction, you will continue with the sloping of the pipe.
  • Begin your trench directly under the pipe for the faucet.
  • Use stakes to mark the placement of your sprinkler heads.
  • Place a bed of gravel inside the trenches.  This helps the water to drain.

Steps to Install an Underground Sprinkler System: Linking the Gate Valve to the Pipes

  • Measure the length of pipe that you will need to connect the gate valve to the bottom of the trench.  Make allowances for the male adapter and the elbow that will be attached to it.
  • Cut the pipe.
  • Cover the threads of the adapters with PTFE plumber’s tape.  Attach the male adapter to the pipe.
  • Attach the elbow to the pipe.
  • Attach the pipe to the gate valve.  You may have to temporarily displace the gravel to do this.  Simply replace the gravel when you are finished.
  • Attach the elbow to the beginning of the pipe run.

Steps to Install an Underground Sprinkler System: Laying the Pipe Run

  • Measure your pipe.
  • Cut your pipe.
  • Then, you are ready to lay your pipe into the gravel-lined trenches.
  • Attach elbows whenever you need to turn corners.
  • Attach T fittings whenever you need to create a branch.  When you use a T fitting, make sure that one of the openings is facing upward.
  • Attach the automatic drain valves (these will allow the water to drain whenever the system is turned off) in the proper places at the end of any branches and at the end of the run.  Use male adapters that have their threads covered with PTFE plumber’s tape.

Steps to Install an Underground Sprinkler System: Attaching the Sprinkler Heads

  • Prepare the risers by cutting them to allow the sprinkler heads to sit flush with the ground, taking into consideration the adapter and depth of the T fitting that will be attached to the riser.
  • Use solvent glue on each adapter that will be attached to a riser.  Make sure that the threads are covered with PTFE plumber’s tape.
  • Allow this to dry before continuing.
  • Attach the T fitting to the risers.
  • Since the riser will need support, place a stake directly next to it.  Attach the stake securely to the riser by placing a small block of wood in between the riser and the stake; use wire to secure them.
  • Place the sprinkler heads in position.

Steps to Install an Underground Sprinkler System: Checking the System

  • Allow 24 hours to pass before checking your underground sprinkler system.  This will allow the solvent to dry thoroughly.
  • Turn the water on.  Inspect the entire length of the pipe run including fittings for any signs of leakage.  Repair any holes or cracks that you detect with plastic solvent cement.  Wrap the repair area with plastic electrical tape.
  • Once you are content that the system works and all leaks have been repaired, fill the trenches in with the dirt.  Top the trenches off with the sod.
  • Enjoy.