Supreme Compression Fittings for PE Pipe: The Complete Guide for Irrigation
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Introduction
Polyethylene (PE) pipe is the most widely used pipe material for irrigation laterals, sub-mains, and flexible connections across UK horticulture and agriculture. Its flexibility, chemical resistance, and ease of handling make it ideal for both permanent buried installations and above-ground seasonal systems.
To connect PE pipe reliably, you need fittings that can grip the pipe securely under pressure without the need for heat fusion or solvent cement. That is exactly what compression fittings do — and the Supreme range is one of the most trusted names in PE compression fittings for agricultural and horticultural irrigation.
This guide covers how compression fittings work, the full Supreme product range available from IrriSmart, and how to make reliable, leak-free connections every time.
How Compression Fittings Work
A compression fitting connects to PE pipe using a mechanical clamping action. The key components are:
- The fitting body — typically manufactured from polypropylene or nylon, with a barbed or tapered internal profile
- The compression nut — threaded onto the fitting body and tightened to compress the pipe against the fitting
- The compression ring (collet or insert) — a toothed or ribbed ring that grips the outside of the pipe as the nut is tightened, preventing pull-out under pressure
When the nut is tightened, the compression ring bites into the outer surface of the PE pipe, creating a mechanical lock that resists both internal pressure and axial pull-out forces. A correctly made compression joint is reliable, reusable, and can be made and remade in the field without specialist tools.
For higher pressure applications and larger pipe sizes, a pipe insert (stiffener) is placed inside the pipe end before fitting to prevent the pipe wall from collapsing under the compression force. Always use inserts where specified by the fitting manufacturer.
The Supreme Compression Fitting Range
IrriSmart stocks the Supreme range of compression fittings, covering all the standard components needed to build and maintain a PE pipe irrigation system. All Supreme fittings are manufactured from high-quality polypropylene and are compatible with standard metric PE pipe sizes used in UK irrigation.
Elbows
Used for changes of direction in PE pipe runs. Available in 90-degree configurations to suit most layout requirements. The compression elbow allows you to change pipe direction without the need for heat bending or additional straight connectors.
Tees
Used for branching off a main PE pipe run to feed a lateral or sub-main. The standard tee connects three pipes of the same diameter, while the reducing tee allows you to branch off to a smaller pipe size — ideal for connecting smaller laterals to a larger sub-main without the need for a separate reducer.
View Supreme Tees | View Supreme Reducing Tees
End Caps
Used to terminate the end of a PE pipe run. Essential for pressure testing a system before connecting drippers or sprinklers, and for capping unused branch connections. The compression end cap can be removed and refitted easily for seasonal flushing.
Ball Valves
Supreme compression ball valves allow you to isolate individual zones or sections of PE pipework quickly and easily. Available in both standard inline configurations and with female threaded outlets for connecting to threaded components such as filters, pressure regulators, or fertigation equipment.
View Supreme Ball Valves | View Ball Valve x Female Thread
Barbed Eco Valve
The Supreme Barbed Eco Valve is a compact, cost-effective shut-off valve designed for use on smaller PE pipe and drip lateral connections. Its barbed connection makes it quick to install without tools, and the simple on/off mechanism allows individual laterals or zones to be isolated for maintenance or adjustment.
Agri Saddles
Saddle fittings allow you to tap into an existing PE mainline or sub-main to add a new branch connection without cutting the pipe. The Supreme Agri Saddle clamps around the outside of the pipe and incorporates a threaded outlet that accepts a standard threaded fitting or valve. Available in single and double outlet configurations to suit different branching requirements.
Saddles are particularly useful for adding new zones to an existing system, or for connecting drip laterals directly to a PE sub-main in the field.
View Supreme Agri Saddle | View Supreme Agri Saddles (twin outlet)
Compression Tools
While many compression fittings can be assembled by hand, a dedicated compression tool makes the job faster, easier, and more consistent — particularly when making large numbers of connections or working with stiffer pipe in cold conditions. The Supreme Compression Tool ensures the nut is tightened to the correct torque, reducing the risk of under- or over-tightening.
View Supreme Compression Tools
Browse the complete PE Compression Fittings and Saddles collection for the full Supreme range.
Choosing the Right Fitting Size
Supreme compression fittings are sized by the outside diameter (OD) of the PE pipe they connect to. Common sizes used in UK irrigation include:
- 16mm OD — drip laterals and small micro-irrigation connections
- 20mm OD — small sub-mains and lateral supply pipes
- 25mm OD — medium sub-mains, common in greenhouse and nursery systems
- 32mm OD — sub-mains
- 40mm and 50mm OD — Sub-main
- 63mm OD — Sub-main
- 75mm OD — Large mainlines
- 90MM OD — Large mainlines
- Upto 110mm OD — Large mainlines
Always measure the outside diameter of your pipe before ordering fittings — do not rely on nominal bore sizes, which can be misleading. PE pipe for irrigation is specified by outside diameter, and the fitting must match the OD exactly for a reliable seal.
Making a Reliable Compression Joint
Follow these steps for a leak-free connection every time:
- Cut the pipe square — use a pipe cutter or sharp knife and ensure the cut is clean and perpendicular. A ragged or angled cut will prevent a good seal.
- Insert a pipe stiffener if required — for pipe sizes 25mm and above, or where specified, insert a stiffener into the pipe end before fitting. This prevents the pipe wall from collapsing under compression.
- Slide the compression nut onto the pipe — thread first, facing away from the pipe end.
- Slide the compression ring onto the pipe — toothed edge facing the fitting body.
- Push the pipe fully into the fitting body — ensure it is fully seated against the internal stop.
- Hand-tighten the nut — thread the nut onto the fitting body and tighten firmly by hand.
- Tighten with a spanner or compression tool — typically one to one and a half turns beyond hand tight. Do not over-tighten, as this can crack the fitting body.
- Pressure test — before burying or covering, pressurise the system and check all joints for leaks.
Maintenance and Reuse
One of the advantages of compression fittings over solvent weld or heat fusion joints is that they can be disassembled and remade. If a joint leaks or a pipe needs to be rerouted, simply undo the compression nut, remove the pipe, and reassemble. In most cases the fitting can be reused, though the compression ring should be inspected and replaced if it shows signs of wear or deformation.
At the end of the season, flush all PE pipe runs and check compression joints for any signs of weeping or movement. Tighten any joints that have loosened slightly due to thermal cycling over the season.
Conclusion
Supreme compression fittings offer a reliable, versatile, and easy-to-use solution for connecting PE pipe in any irrigation system. With a comprehensive range covering elbows, tees, saddles, valves, and end caps, you have everything you need to build, extend, or repair your PE pipework on site.
Browse the full Supreme PE Compression Fittings and Saddles range at IrriSmart, or contact our team for advice on specifying the right fittings for your system.