PEX expansion fittings

Entry in Joining methods · Updated October 29, 2026 · Written by the Know Your Pipes editors from the sources listed under References

PEX expansion fittings are cold expansion fittings that join PEX tubing by stretching the tube end, slipping the fitting in, and letting the tube's elastic "memory" shrink it back tightly over the fitting.^[3] No heat, solder or crimp ring is involved.

Two ASTM standards cover the method. ASTM F1960 uses a PEX reinforcing ring over the tube end, and ASTM F2080 uses a metal compression sleeve drawn over the joint after the tube has shrunk onto the fitting.^[3]

1 How the joint is made

In an F1960 joint, a PEX ring is placed over the tube end and an expander tool stretches the tube and ring together.^[3] The fitting goes into the enlarged end, and over a short time the tube and ring recover toward their original size and grip the fitting's ribs.^[3] One maker summarizes it as holding the fitting in place until the tube and ring memory secure the connection.^[4]

In an F2080 joint, the tube is expanded and pushed over an oversized fitting, it shrinks down, and a tool then pulls a metal sleeve over the joint to compress the tube onto the fitting.^[3]

Expansion relies on the tube being able to stretch and recover, which is why the method is mainly used with PEX-A tubing. One maker's F1960 fittings are designed for its PEX-A tubing and are not to be used with that maker's other PEX product.^[4] Another maker's rings are listed for PEX-A plumbing systems with a degree of crosslinking of 70% to 89%.^[5]

F1960 lists residential and commercial drinking water, sealed central heating and under-floor heating among its uses.^[1] F2080 adds municipal service lines, radiant and hydronic heating, snow and ice melting, and geothermal piping.^[2] Both standards also cover PE-RT tubing.^[1][2]

2 Tools, cold weather and faults

With a working tool and correct technique, the stretch on the tube is even, leaving no path for leaks.^[4] One maker calls for a 1/8 turn between expansions and says manual tools are not recommended for its system.^[4] Another says to rotate its manual expander a quarter turn after each expansion to prevent grooves, and to allow no more than 1/16 in of ring overhang past the tube end on rings without a stop.^[5]

Cold slows the shrink-back. One maker says to keep rings at about 55°F or warmer so they expand evenly, and to expand slowly and only as far as needed in cold conditions.^[4] Another says its connections must be made above 5°F.^[5]

The same instructions list the usual causes of a bad joint: a tube that was not cut square, a fitting not pushed fully into the expanded tube and ring, a ring that does not fully cover the tube end, and a cut or grooved sealing barb.^[4] That maker states its fittings are reusable if the barb is undamaged.^[4]

3 Related methods

Expansion fittings have a different shape from the insert fittings used with PEX crimp rings and PEX clamp rings, so the two families are not interchangeable at the same joint. General properties of the tubing are covered under PEX pipe.