PEX crimp rings

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

A PEX crimp joint is made by squeezing a copper crimp ring around PEX tubing that has been pushed over a ribbed insert fitting, so the tube is pinched against the fitting's barbs.^[2] One maker describes its copper crimp system as proven over more than 30 years of use.^[4] The method joins PEX pipe with PEX-A, PEX-B and PEX-C tubing when the fitting maker lists that tubing. The same crimp tools were used on polybutylene pipe installations.^[3]

The insert fitting carries the seal: it has barbed or ribbed annular ends, and the ring supplies the squeeze.^[2] Fittings may be brass, copper, bronze or plastic.^[2]

1 Standards

ASTM F1807 covers metal insert fittings with copper crimp rings for PEX and PE-RT tubing from 3/8 in to 2 in, rated for 100 psi hot- and cold-water systems at temperatures up to 180°F.^[1] The same standard allows stainless steel clamps as an alternative to the copper ring; those are described under PEX clamp (cinch) rings.^[1]

Plastic insert fittings with copper crimp rings are made to ASTM F2159, which covers 3/8 in to 1 in.^[2] A third standard, ASTM F2434, covers metal insert fittings that add O-rings under a copper crimp ring.^[2]

2 Making and checking the crimp

The ring is slid onto the tube, the tube is pushed over the fitting to its shoulder, and the ring is moved back down over the ribs before a crimp tool closes it.^[2] One maker sets the ring 1/8 to 1/4 in back from the tube end for 3/8 in to 1 in sizes, which generally centers it over the fitting's ribs.^[4] One maker's hand tool instructions allow one crimp per ring.^[3]

The finished ring is checked with a go/no-go gauge.^[2] The "Go" slot has to pass freely across the crimped ring anywhere except the small bumps where the jaws met, and the "No-Go" slot must not pass anywhere.^[3] A joint that fails either check is cut out and remade with a new fitting and ring after the tool is adjusted.^[3]

The limits above are the ASTM crimped-ring diameters printed in one maker's tool sheet, which also caps out-of-round variation at 0.006 in.^[3] Crimp tools wear with use and the crimp diameter slowly grows, so hand tools have an adjustment for tightening them back into range.^[3]

3 Larger sizes, cold weather and burial

For 1 1/4 in to 2 in tube, one maker uses powered crimp tools, sets the ring further back from the tube end, and supplies only a "Go" gauge for the 2 in size.^[4] The same maker reports that no more than two re-crimps are needed for a good crimp at temperatures as low as 5°F and does not recommend crimping below 5°F.^[4]

When a brass crimp fitting must be buried directly in soil, that maker recommends covering the fitting and ring with a heat-shrink sleeve, foam pipe insulation or several layers of plastic film, and advises against burying the fittings in concrete.^[4] Brass fittings and water chemistry are covered under brass fittings and dezincification.

4 Comparison with other PEX joints

Crimp joints share their insert fittings with stainless clamp rings, while PEX expansion fittings use a different, wider fitting and need no ring compression tool.^[2] Supply houses stock crimp tools, rings, gauges and cutters by size; PlumbingSupplyAndMore's PEX tools category (PlumbingSupplyAndMore has the same owners as this reference) is one example of a supply-house listing. Crimping is a permanent connection; the fitting maker's instructions and local code govern where crimp joints may be concealed or buried.