What Are The Common Sizes Of PEX-AL-PEX Compression Fittings Available
2026-01-23
When planning a plumbing or hydronic heating project using multilayer pipe, one of the most critical questions is: What are the common sizes of PEX-AL-PEX compression fittings available? Choosing the correct fitting size is fundamental for ensuring a leak-free, durable, and code-compliant system. At SUNPLAST, we specialize in high-performance piping solutions, and understanding the standard sizing for these robust fittings is key to a successful installation. PEX-AL-PEX compression fittings are designed to create secure, metal-to-metal connections with the aluminum core of the pipe, offering superior reliability.
The sizing of these fittings corresponds directly to the outer diameter (OD) of the PEX-AL-PEX pipe they are designed to connect. The most widely used sizes in residential and commercial applications are as follows:
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16mm (or 3/8"): Commonly used for supply lines to individual fixtures like faucets and for some radiant heating loops.
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20mm (or 1/2"): The standard size for main domestic water supply branches and many radiant heating panel circuits.
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26mm (or 3/4"): Typically used for main water trunk lines and larger radiant heating mains to reduce pressure drop.
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32mm (or 1"): Employed for primary building supply lines, large volume applications, and commercial heating systems.
For a clear overview, here is a table detailing the common sizes and their primary applications:
| Fitting Size (Metric / Imperial) | Typical Application |
|---|---|
| 16mm (3/8") | Fixture supply lines, compact radiant loops |
| 20mm (1/2") | Branch water lines, standard radiant heating circuits |
| 26mm (3/4") | Main water trunks, primary heating headers |
| 32mm (1") | Building mains, commercial system lines |
PEX-AL-PEX Compression Fittings FAQ
What is the difference between metric (mm) and imperial (inch) sizes for these fittings?
The difference is primarily a regional standard. European and international markets typically use metric sizing (e.g., 16mm, 20mm), while North American markets often use imperial (e.g., 1/2", 3/4"). It is crucial to match the fitting size precisely to the outer diameter of your specific PEX-AL-PEX pipe. SUNPLAST provides clear specifications on all packaging to prevent confusion.
Can I use a standard PEX crimp tool on PEX-AL-PEX compression fittings?
No, you cannot. PEX-AL-PEX compression fittings require a two-part compression nut and sleeve that compresses onto the pipe's aluminum layer. They are installed using two adjustable wrenches. Using a standard PEX crimp ring tool on multilayer pipe will not create a proper seal and will likely result in a leak or system failure.
Are all PEX-AL-PEX compression fitting brands compatible with all pipe brands?
While sizes are standardized, we strongly recommend using fittings and pipe from the same manufacturer or a certified compatible system, like those from SUNPLAST. This ensures perfect dimensional tolerance, matching engineering specifications, and optimal seal integrity, preserving your system's warranty and performance.
Selecting the right size fitting is the first step toward a reliable installation. For guaranteed compatibility, performance, and access to our full technical support, always choose genuine SUNPLAST PEX-AL-PEX compression fittings and components.
Contact us today for detailed technical datasheets, a comprehensive size guide, or to speak with our expert team about your specific project requirements. Ensure your next build is backed by the precision and quality of SUNPLAST.
