Clamp (Cinch) PEX Fittings: Definition & Technical Guide
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Clamp fittings, also called cinch fittings, are a PEX pipe connection method that uses a stainless steel cinch clamp tightened around the outside of the PEX tubing over a barbed brass or poly-alloy insert fitting to create a watertight seal. Clamp fittings are one of three primary PEX connection systems alongside crimp rings and expansion fittings, and they are distinguished by their use of a single-ear stainless steel band secured with a dedicated cinch clamp tool.
Single Ear Compression, Tool Versatility & PEX-A/B/C Compatibility
The clamp fitting connection works by compressing the PEX tubing onto a barbed insert fitting. The plumber slides the stainless steel cinch clamp over the PEX tubing, inserts the barbed fitting into the tubing bore, positions the clamp over the fitting’s barb area, and compresses the clamp’s ear tab using a cinch clamp tool. The tool squeezes the single ear flat, uniformly tightening the band around the tubing and locking it in place.
Cinch clamps work with all three PEX types (PEX-A, PEX-B, and PEX-C) and require only one tool size regardless of pipe diameter, making them popular among plumbers who work with multiple PEX sizes on the same job. The stainless steel band resists corrosion and maintains clamping force over the service life of the system.
The primary advantage of clamp fittings over copper crimp rings is tool versatility. A single cinch clamp tool works on all PEX sizes from 3/8 inch to 1 inch, while crimp ring tools require a separate die or tool head for each pipe size. This makes cinch clamps more economical for plumbers who need to carry fewer specialized tools.
Standard Cinch Clamps, Brass, Poly-Alloy & Stainless Insert Fittings
Standard cinch clamps are single-ear stainless steel bands available in sizes from 3/8 inch to 1 inch to match PEX tubing diameters. The ear tab provides the compression point for the cinch tool.
Brass insert fittings are the most common barbed fitting material used with cinch clamps. Brass fittings provide durability and corrosion resistance but may not be suitable for aggressive water chemistry.
Poly-alloy (PPSU) insert fittings are engineered plastic fittings that resist dezincification in aggressive water conditions. These are preferred in areas with low pH or high chloride water.
Stainless steel insert fittings offer the highest corrosion resistance and are used in demanding applications or where water chemistry is unknown.
Repiping Projects, Tight-Space Access & PEX Installation Services
PEX clamp fitting installation is a core component of modern residential plumbing work, particularly during whole-house repiping and new construction. Bonded Plumbworks provides pipe repair and repiping services that include PEX installation using clamp, crimp, and expansion connection methods selected based on project requirements and pipe accessibility.
During a repiping project, Bonded Plumbworks’ plumbers evaluate the connection method best suited to each area of the home. Clamp fittings are especially useful in tight spaces where the compact cinch tool can reach connections that larger crimp or expansion tools cannot access. For bathroom plumbing and kitchen plumbing renovations, PEX with clamp fittings reduces installation time compared to soldered copper connections.
ASTM F2098, ASTM F1807, ASTM F2159 & NSF/ANSI 61 Standards
PEX clamp fittings must comply with ASTM F2098 (Standard Specification for Stainless Steel Clamps for Securing SDR9 Cross-Linked Polyethylene Tubing to Metal Insert and Plastic Insert Fittings). Insert fittings must meet ASTM F1807 (brass) or ASTM F2159 (poly-alloy). The applicable state building codes permits clamp fittings for PEX connections in potable water systems. All PEX fittings and clamps must carry NSF/ANSI 61 certification for contact with drinking water.
Oetiker StepLess, Watts & SharkBite Cinch Clamp Systems
Oetiker manufactures the StepLess single-ear clamp series used widely in PEX plumbing. Watts produces brass and poly-alloy PEX insert fittings compatible with cinch clamps. SharkBite offers cinch clamp tool kits with assorted clamp sizes. Apollo manufactures stainless steel cinch clamps and a full line of PEX insert fittings.