When planning a lawn or garden irrigation system, the choice of piping is a
critical decision. For decades, PVC and polyethylene (poly) pipes have been the
standard. However, PEX pipe has emerged as a powerful contender in the plumbing
world, leading many homeowners to ask: Can I use PEX pipe for irrigation?
The short answer is yes, but with some important considerations. This
comprehensive guide will explore everything you need to know about using PEX for
your irrigation project, helping you determine if it's the optimal solution for
your needs.
What is PEX Pipe?
PEX, or Cross-linked Polyethylene, is a flexible, durable plastic tubing
that has revolutionized residential plumbing. Its strength and resistance to
heat and chemicals make it ideal for hot and cold-water supply lines inside
homes. This versatility naturally leads to questions about its application
outdoors.
Benefits of Using PEX for Irrigation
PEX offers several advantages that make it attractive for irrigation
systems:
Freeze Resistance: This is a significant advantage. PEX is flexible and can
expand, making it more resistant to bursting if water inside freezes
unexpectedly. While not foolproof, it's more forgiving than rigid PVC.
Flexibility and Easy Installation: PEX tubing can bend around corners and
obstacles, reducing the number of fittings and connections required. This means
fewer potential leak points and a faster, easier installation process.
Corrosion and Scale Resistance: Unlike metal pipes, PEX will never corrode
or rust. It is also highly resistant to scale build-up, ensuring consistent
water flow over time.
Cost-Effective for Complex Runs: For systems with many turns, the
flexibility of PEX can save money on elbow fittings and labor time compared to
PVC.
Important Drawbacks and Considerations
Despite its benefits, PEX is not a perfect fit for every irrigation
scenario. Be aware of these key limitations:
UV Sensitivity: This is the biggest drawback. PEX is not designed to be
exposed to direct sunlight for prolonged periods. Ultraviolet (UV) rays can
degrade the material, making it brittle and reducing its lifespan. PEX used for
irrigation must be buried underground.
Not for Main Pressure Lines: While PEX handles typical household water
pressure well, it is generally not recommended for the high-pressure main supply
line from the street to your house. A more robust pipe like HDPE or PVC is
better suited for that task.
Rodent Damage: In some areas, burrowing rodents may find PEX appealing to
chew on. While not a universal problem, it's a risk that doesn't exist with
harder materials like PVC.
How to Install PEX Pipe for an Irrigation System
If you've decided PEX is right for you, follow these general steps:
Plan Your System: Sketch out your garden, marking zones, sprinkler heads,
and the path of the pipes.
Trenching: Dig trenches to the required depth (below the frost line in cold
climates).
Lay the Pipe: Unroll the PEX tubing along the trenches. Use PEX-specific
fittings (brass or plastic) and a cinch-clamp or crimp-ring tool to make secure
connections to manifolds, valves, and sprinkler headers.
Connect to Water Source: Connect your main line (preferably PVC or poly) to
the PEX manifold using the appropriate adapter.
Flush and Test: Before attaching sprinkler heads, flush the system to
remove any debris. Then, pressurize the system and check all connections for
leaks.
Backfill: Once you've confirmed there are no leaks, carefully backfill the
trenches.
Frequently Asked Questions (FAQ)
Q1: Can PEX pipe be used above ground for irrigation?
A: It is not recommended. PEX degrades under UV light from the sun. If an
above-ground section is unavoidable, it must be insulated and shielded from
direct sunlight.
Q2: What type of PEX is best for irrigation?
A: PEX-A, PEX-B, and PEX-C are all suitable. PEX-A has the highest
flexibility, which can be helpful. For irrigation, where hot water isn't a
concern, PEX-B is a common and cost-effective choice.
Q3: Is PEX safe for drinking water?
A: Yes, PEX tubing used in North America and Europe is certified to
NSF/ANSI 61 standards for potable water. This means it's safe for drinking
water, which is a plus for vegetable garden irrigation.
Final Conclusion
PEX pipe is a viable and excellent option for the underground lateral lines
of a residential irrigation system, especially in regions with cold winters. Its
flexibility and freeze resistance are major benefits.
However, its UV sensitivity means it cannot be used above ground. For the
best results, many professionals recommend a hybrid approach: use a durable pipe
like PVC or HDPE for the main supply line and more vulnerable sections, and
leverage the flexibility of PEX for the branch lines feeding your
sprinklers.
By understanding its strengths and limitations, you can confidently decide
if PEX is the right pipe to help your garden thrive.
