Irrigation plays a crucial role in agriculture, ensuring that crops receive the necessary water for growth and development. One of the key components of modern irrigation systems is the pipe, which has evolved significantly over time.
In this article, I will explore the importance of pipes for irrigation in agriculture, including the types of pipes used, factors to consider when choosing irrigation pipes, maintenance and care tips, and the future of irrigation.
How to Select the Proper Pipe for Irrigation
When setting up a new irrigation system or upgrading an existing one, one of the most important decisions is choosing the right type of pipe for irrigation. There are several key factors to consider, such as pipe material, diameter, pressure rating, durability, and flexibility.
Types of pipe used for irrigation
PVC Pipes
Polyvinyl chloride (PVC) is one of the most widely used types of pipes for irrigation systems. PVC for irrigation comes in sizes from 1/2″ to 12 inches in diameter, depending on your water flow needs.
They are extremely strong, durable, and resistant to damage from freezing, thawing, and chemical corrosion.
PVC is highly resistant to UV rays from the sun, so it can be directly buried in soil or used above ground without additional protection. It is relatively inexpensive and easy to assemble using glue-based PVC fittings. For these reasons, PVC pipe is often the best choice for residential and small-scale agricultural irrigation systems.
Polyethylene (PE) Pipes
Polyethylene, also called PE or poly pipe, is another popular material for irrigation pipes. It is available in high-density polyethylene (HDPE) and cross-linked polyethylene (PEX) varieties.
HDPE pipe is extremely durable and resistant to corrosion, with a high resistance to stress cracking. It can withstand temperatures ranging from -50 to +77 degrees Celsius. HDPE is extremely flexible, allowing it to be coiled for transportation and insertion into directional drills.
HDPE pipes are capable of withstanding high pressures, making them suitable for sprinkler systems with pressures over 100 psi. Though more expensive than PVC, HDPE pipes have a lifespan exceeding 50 years. They are very commonly used for agricultural irrigation on large farms and rural areas.
Copper Pipes
Soft copper pipes are still occasionally used for irrigation, though they have largely been replaced by more affordable plastic alternatives. Copper delivers high flow rates efficiently and has an extremely long estimated lifespan of over 50 years when used for carrying water below ground.
Copper is expensive. It is prone to corrosion from fertilizers and some soils. It also requires soldered fittings, which are more complex to install than glued plastic joints. It may still be used where aesthetics are important or backflow prevention is needed from high water pressure systems.
Galvanized Steel Pipes
Galvanized steel pipes, sometimes called iron pipes, are durable and pressure-rated. But they are prone to rusting over time unless painted or protected. They are most commonly used for large-scale agricultural irrigation. Higher water pressures and flow volumes are required to irrigate expansive farmland.
Steel has a smooth inner surface and can withstand pressures over 200 psi. It is very strong and able to carry enormous water volumes through diameters up to 36 inches. Steel also allows for easy insertion of valves and fittings.
With maintenance, steel can endure for 30–40 years, but it requires more upkeep than PVC or HDPE pipes.
Other Options
Concrete, clay, and stoneware pipes have also been used for irrigation in the past. However, today, they are much less commonly used, except in some specialized applications.
Fiberglass-reinforced plastic (FRP) is UV-resistant and non-corrosive, making it well-suited for above-ground use. Flexible, porous hoses and tubing are widely used for drip irrigation. They deliver water directly to the plant roots.
Factors to Consider When Choosing Irrigation Pipe
There are several important factors to weigh when deciding which type of pipe is best for a particular irrigation system:
Pressure Rating
The pressure rating indicates the maximum pounds per square inch (psi) of water pressure the pipe can withstand before failing. This depends on both the pipe material and additional specifics like wall thickness.
Pipe scheduled for underground installation generally requires a higher rating than above-ground pipe.
Diameter
Larger-diameter pipe can carry greater water volumes but is more expensive and difficult to install. The minimum diameter needed depends on factors like source water volume, number of sprinklers, and landscape area.
Pipe Schedule
Certain materials, like PVC, come in varying schedules that indicate the wall thickness. Schedule 40 is a common choice that provides adequate strength for many applications. Schedule 80 is thicker-walled for higher-pressure systems or where the pipe may be exposed to physical damage.
Flexibility
Rigid pipe like PVC cannot flex or bend easily, so it requires straight trenches and more fittings for turns. Flexible polyethylene pipe can bend in trenches, reducing labor and fitting costs.
Durability
Buried pipe must withstand soil stresses, environmental factors, and potential damage from roots over many years. Materials that are durable and resistant to chemicals and UV light from the sun will provide reliable, long-term service.
Cost
Flexible polyethylene may have a lower per-foot cost. However, PVC requires fewer repairs due to its durability and ability to withstand pressure surges. Total installed costs factor in materials, labor, and longevity. They determine the most affordable solution.
Installing Irrigation Pipes
With the right pipe material selected, it’s important to properly install it to ensure an efficient irrigation system. Here are some best practices:
Trenching
Trenches for horizontal pipes should be dug at least 6 inches deeper than the pipe diameter to allow for cover and settling. Trenches for vertical pipes extending aboveground need to terminate a few inches above the surface.
Pipe Layout
A pipe layout designating supply and return lines, zones, and sprinkler placement simplifies installation. Main lines are usually laid out first, with laterals connecting to T-fittings or valves.
Fittings
Glue fittings like PVC cement or solvent weld connectors produce strong, water-tight joints. For polyethylene, compression or insertion fittings that don’t require open flames are used.
Pipe Placement
Roll out or lower the pipe carefully into the trench to avoid scratches or kinks that can cause leaks. Fill any gouges or cuts with solvent before installation.
Grade
Laying pipe on a consistent, slight downgrade slope (1/4–1/2 inch per 100 feet) allows water to drain and air to escape from the system.
Support
Support pipes every 4–5 feet using compacted soil or commercially available chairs to prevent the weight of the backfill from causing sagging or misalignment.
Backfilling
After testing hydrostatically for leaks, trenches can be backfilled. Use the native soil and compact it in thin layers to prevent air pockets or damage to the pipe.
Maintaining and Caring for Irrigation Pipes
Proper maintenance keeps an irrigation system running smoothly.
Flushing Pipes: Periodically flushing pipes with an anti-drain valve removes sediment from water that enters the system. This keeps sprinkler heads from clogging.
Protecting Against Freezing: Draining above-ground pipes in the fall and blowing out below-ground lines with compressed air prevents damage from expanding ice in colder climates. Insulation may also be needed for exposed piping.
Checking for leaks: Walking the system when first turned on each season or after spikes in usage or pressure allows detection of small leaks before they worsen. This extends the life of seals and joints.
Repairing Damage: Damaged sections of pipe are replaced with new pipe fitted using the appropriate materials for the application. Clamps can temporarily fix small leaks while a more permanent repair is scheduled.
Root Prevention: Applying root killer chemicals or installing root barrier materials around pipes protects against roots entering the lines through microscopic openings in pipe walls over time. Compressing soil tightly during the backfilling process also deters root growth.
Draining in Fall: Drip irrigation systems require flushing any chemicals and draining lines completely of residual water before freezing weather arrives to prevent damage over the winter months.
Specific Applications and Installations
Beyond basic residential use cases, irrigation pipe has a variety of other applications involving specific materials and installation techniques.
Home Lawn and Garden Irrigation
For smaller yards and gardens, DIY-friendly polyethylene or PVC pipe laid out in straight lines across landscaped areas works well. Multiple zone valves activate groups of sprinkler heads for proper water coverage.
Farm Irrigation Systems
Large agricultural operations require pipes that can withstand higher pressures over longer distances. Heavy-duty poly or steel pipe forms the mainline, with pressure-compensating lateral lines branching out in evenly-spaced rows across fields. Precise water control is critical for crop production.
Golf Course Irrigation
Undulating turf areas pose challenges like maintaining consistent pressure along hilly fairways and greens. Specialized tubing materials like polyurethane and dripline are well-suited. GPS mapping of heads assists with programming complex zone systems.
Pipeline Repairs
Replacing damaged sections requires excavation with caution to avoid further issues. Common fixes for leaks involve cutting out the bad portion of PVC or poly and installing new pipe joined with appropriate fittings or clamps as a temporary fix.
Proper application of the right irrigation pipe materials allows each of these systems to distribute water uniformly according to the unique needs of the landscape, farm fields, or golf course they serve.
FAQs About Pipe for Irrigation Systems
How deep should irrigation pipes be installed?
The minimum recommended depth is 18–24 inches below ground to protect from freeze damage, direct sun exposure, and accidental impacts from tillage or future digging. Consider local codes and freeze lines for your climate.
What size pipes will I need to irrigate my 1-acre property or vegetable garden?
Most residential systems use 0.5–1 inch mainlines for coverage up to 0.5 acres. Over 1 acre, 1.25-2 inch mainlines may be needed depending on the number of zones, soil type and plant water needs. Consult irrigation designers for specific recommendations.
What size pipe do I need for my property?
Pipe sizing depends on water source GPM, number of sprinkler heads, and landscape area. An irrigation professional can help design the appropriate flow rate and diameters.
How can I winterize my irrigation pipes?
For PVC or poly pipe, blow out water with compressed air in the fall. Drain and disconnect hoses. Insulate exposed above-ground pipes to prevent freezing.
How deep should irrigation pipes be buried?
Main lines should be buried at least 1 foot deep, with laterals at 6–8 inches, to protect them from sunlight, frost heaving, and physical damage. Deeper is better in colder climates.
Conclusion
Irrigation pipe is a fundamental but often overlooked component of any watering system. Taking the time to fully research pipe material options, consider critical design factors, and professionally install the correct piping lays the groundwork for an irrigation setup that endures.
Forward-thinking practices such as root barriers and protective insulation on exposed pipes can counteract deterioration and prolong function for decades.
With the importance of water conservation always top of mind, effective irrigation pipe installation allows precise distribution exactly where it is needed, minimizing waste.
Following the best practices covered here, you can easily choose the best pipe for your irrigation system.