I enjoy sharing my knowledge and experience about lawn care, composting, and other gardening tips.
Setting Up a Homemade Underground Sprinkling System With PEX Is Easy
Building an underground PEX sprinkler system for lawn or garden irrigation is a very easy thing to do. Explaining how to install this buried sprinkler system is actually much more difficult than doing the job itself.
PEX is approved for underground usage. It is also subject to failure when frozen, but it seems to be less likely to fail compared to PVC pipe. I am not a plumber and was able to complete this project easily. The hardest part is digging the trench in which to bury the PEX pipe.
- 1/2 Inch PEX Pipe
- 3/4 Inch PEX Pipe
- 3/4 x 3/4 x 1/2 Inch PEX Tee (One needed for every sprinkler.)
- 3/4 x 3/4 x 3/4 PEX Tee (Just one needed.)
- 1/2 Inch PEX Plastic Clamps
- 3/4 Inch PEX Plastic Clamps
- 1/2 Inch PEX x MNPT Elbows (Ensure you purchase the same MNPT size as the sprinkler head, typically 1/2 or 3/4 inch. One needed for every sprinkler.)
- Sprinkler Heads
- Teflon Pipe Tape
- Garden Hose to 3/4 Inch PEX adapter
- 6 foot Piece of Garden Hose
- 3/4 x 3/4 MNPT PEX Adapter
- 3/4 Inch Hose Mender
- Flathead Screwdriver
- PEX Pipe Cutter
Planning Your Sprinkler System
One of the most important parts of building a lawn and garden sprinkler system is the design. Designing a system that provides even watering across your lawn will give a more uniform appearance and a healthier lawn. If the sprinkler heads aren't placed correctly, dry spots will develop and lead to stunted growth. Over-watered spots may be susceptible to disease, or will outgrow other areas.
Head-to-Head Sprinkler Coverage
Head-to-head sprinkler coverage is considered to be the goal when designing your system. This means that each sprinkler should be able to throw water far enough to reach, or be close to, the next sprinkler.
One of the benefits of PEX is that it is easily adapted after it has been installed, creating a custom sprinkler design based on your lawn needs. You are able to modify existing sprinkler heads easily using the same techniques as when it was first installed. Due to this feature, you are able to install the outline of your system and then turn it on to find where the coverage is poor. It is then very easy to add a sprinkler exactly where it is needed.
Before You Dig
Whenever you dig anywhere that has any chance of having underground wires or pipes of any kind, contact your local government to mark these locations so that you do not inadvertently damage them. In my area, calling 411 will reach the correct department. These people will schedule someone to come out and mark the locations where care is needed.
1. Dig a Trench
Dig a trench about the height of your sprinkler beginning from your water source. Continue trenching near to the external border of the zone you are working on. Ensure that you remain a few inches from the very edge of your lawn. This is to prevent you from inadvertently striking your PEX pipe with an edger. This is a good time to have some friends come over or encourage your children to help dig around the areas that do not have buried wires.
In areas that have buried wires, dig up about 1 foot from either side of the markings placed. Use a garden hose and a length of PEX pipe to direct water to "bore" through the soil and continue the trench. This should not damage the buried wires.
2. Place Main Line
Run 3/4 inch PEX along inside the trench you have dug. PEX is flexible and will bend around corners easily, unlike most PVC. Run your 3/4 inch PEX underneath/through any holes you bored using a water hose. Run your PEX all the way through the trench until it completes a circuit at the beginning of the trench.
3. Preparing to Add Sprinklers
Using the PEX Cutting tool cut where you want a sprinkler to be placed. Place a 3/4 inch plastic clamp on either side of the cut pieces. Place a 3/4 x 3/4 x 1/2 inch tee in both openings of the PEX pipe.
Push the clamps over the pipe with the plastic PEX inside and clamp it down using pliers. It should look like the series of pictures below. It will be easier to use a larger set of pliers or tongue and groove pliers ("Channellocks") to snap the plastic PEX clamps down. If the clamp isn't correctly placed, you can release it using a twisting/levering motion with a flat head screwdriver.
4. Placing a Sprinkler
Once the tee is in place, cut a section of 1/2 inch PEX pipe to where you want your sprinkler to be. Place a 1/2 inch PEX clamp on either side of the pipe. Feed a 1/2" to MNPT tee onto one end and clamp it down. Wrap the MNPT portion in Teflon tape and screw a sprinkler head onto the MNPT fitting. Put the open end onto the 1/2" portion of the 3/4 x 3/4 x 1/2 fitting on the main line, feed the clamp over the 1/2" portion and clamp it down with pliers. Below is a mock-up showing how each piece is placed. Place the four corner sprinklers in this manner.
5. Attach Controller
Choosing a controller for your sprinkler system can be a daunting task. There are many companies and options. I chose one as simple as possible, which connects right up to a standard garden hose outlet. Consider choosing a multi-zone model, so that you can expand your sprinkler system in the future, such as to water a garden or your back yard.
As an aside, I do not recommend this Melnor Controller. The first one (pictured below) would not connect to my phone and was replaced under warranty. The second one worked, mostly, but the buttons would activate and then close without emitting water sometimes. This was unfortunate, but sometimes technology fails. However, what finally did it in was pulling too much on a hose I had attached, which sheared it off at the main connection, ruining the whole controller.
Using the section of garden hose, screw one end to your controller. Using the PEX cutting tool, cut enough hose to comfortably reach the ground and the beginning of your 3/4 inch main line. Install the hose mender onto the cut end of the hose. Screw the garden hose to 3/4 PEX adapter into the end of the garden hose mender. Attach the main line to the hose using a 3/4" PEX clamp. See the series of pictures below.
Connect the main line back to itself using the single 3/4 x 3/4 x 3/4 Tee, completing the circuit.
6. Run Sprinkler System and Adapt
Many pop-up sprinkler heads are able to be adjusted. If yours are, turn them all to maximum pressure/throw. Adjust the spraying arc so that you aren't watering your driveway or spraying water onto your house. Note where there are dry spots, or where you aren't getting head-to-head coverage. These are areas where you should add additional sprinkler heads. Continue testing and modifying your system after every sprinkler head is added, to ensure your water system can still supply enough pressure. Aim to get each sprinkler head just above ground level, but below the height in which you will be cutting your lawn.
Once you are satisfied with how your sprinkler system is installed, it's time to clean up. I recommend refilling any holes and the trench first so you are less likely to trip and fall during the clean-up process. Ensure that no part of the PEX is exposed to sunlight, as standard PEX will begin to become brittle and crack or fail in some manner after some time. Clean up and throw out any trash.
Zoning Your Lawn Sprinkler System
One of the limiting factors for large lawns is the number of sprinklers your water pressure is able to support. Larger lawns will need to be broken down into watering zones. Each zone should be watered at a different time.
Based on overlap and your local laws or ordinances, it might be beneficial to water them on different days. Any over-spray from a zone would benefit the other one.
When Should You Water Your Lawn?
Water your zones at different times. This will prevent too much water pressure loss during watering times. If your local ordinances allow, water your zones on different days. Finally, water in the very early morning or late at night. This will decrease the amount of water lost to evaporation.
Tuning and Troubleshooting
One of the strengths of PEX is that it is easily changed after the fact. The 3/4 x 3x4 x 1/2" fittings can rotate along their axis, allowing you to move your sprinkler to either side of the main line if desired. Rotate the 1/2x1/2 MNPT fitting 180 degrees to point the sprinkler upwards as well.
If you find that the sprinklers aren't receiving full pressure, such as not popping up fully, try lower-flowing sprinkler heads. I purchased Hunter MP rotators to replace all of my sprinkler heads due to low flow issue. They flow much less water, increasing pressure across the line. Hunter MP rotators will need to be used longer but will be less likely to cause excessive runoff. More water will get into the soil. They also spray evening along their entire water throw. Even though there is a special tool to change the arc, it is possible to use a flat head screwdriver to change distance and water arc.
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2021 Devin Gustus