How to Make PEX Crimp and Clamp Joints and Check Them

Why this matters

An under-crimped ring holds static pressure on test day and lets go months later, after thousands of valve closures have worked the pipe against the barbs. From three feet away a good crimp and a bad one look identical. The gauge is the only thing that tells them apart, and the shops that get crimp callbacks are almost always the ones that gauge a sample instead of every ring. The case this card exists to prevent is written up in The PEX Crimp That Let Go Behind the Vanity.

Two ring systems, two tools, one rule

Copper crimp ring. A plain copper band compressed evenly all the way around by a crimp tool with round jaws sized to the pipe. Rings and metal insert fittings are made to ASTM F1807; plastic insert fittings to ASTM F2159. The finished ring is proved with a go/no-go gauge.

Stainless clamp ring. Often called a cinch or pinch clamp: a stainless band with a raised ear, made to ASTM F2098, closed by a pincer tool that squeezes the ear until the tool's ratchet releases. Proof is the ear closed to the ring maker's check, which on many systems is a gauge of its own.

The rule that ties them together: the pipe, the fitting, the ring and the tool must all be combinations the pipe maker lists, and the two systems do not cross. A copper crimp tool on a stainless ring, or a pincer on a copper ring, can make a joint that holds on test and is still not a listed joint. Matching the print on the pipe and fittings to the tool is the job of Reading PEX Pipe and Fitting Markings Before You Join. Do that read before the first cut, not after the fifth ring. Cold expansion is a different joint with its own card.

Before the first joint

Calibrate the crimp tool at the start of each day and after any drop. Make a test crimp on scrap pipe and a scrap fitting, gauge it in two directions, and adjust the tool by its maker's method if it fails. Jaws wear and adjustment drifts, and a tool that was right last week can make a row of under-crimped rings today. Write the check on the job ticket with the time.

Check the clamp tool's release the same way. A pincer out of adjustment can release before the ear is fully closed. Close a ring on scrap and check the ear against the maker's gauge or mark.

Cut square with a sharp PEX cutter. A skewed cut leaves one side of the pipe short of the fitting shoulder, so on that side the ring can sit over pipe with no barb under it. A dull cutter crushes the pipe oval and leaves a lip that rolls under on the barbs.

Hazards at this stage: the cutter's blade is open in your hand, so cut away from the other hand and close it between cuts. A crimp tool closes with enough force to break a finger caught in the jaws or between the handles, so both hands stay on the grips and nobody steadies the pipe near the jaws.

Making a copper crimp joint

1. Ring on first, then push the pipe fully onto the fitting until the pipe end butts the shoulder. The barbs hold the joint, not the shoulder, but a pipe stopped short puts the ring over a section with no barb under it. Skip it and the ring can pass the gauge and still pull off.
2. Set the ring 1/8 to 1/4 in back from the pipe end, measured from the ring's near edge to the end of the pipe. That window puts the ring over the barbs. A ring pushed against the shoulder crimps the shoulder; a ring set too far back crimps pipe past the last barb. Most pipe and fitting instructions state this window, and where theirs differs, theirs governs.
3. Hold the tool square to the pipe, jaws centered on the ring, and close it fully until the handles meet or the stop is reached. A tilted tool crimps an oval, which can pass the gauge in one direction and fail it 90 degrees away.
4. Gauge every ring, in two directions. The GO slot must slide over the crimped ring and the NO-GO slot must not. Check once, rotate the gauge a quarter turn around the pipe, check again. GO will not slide over means under-crimped. NO-GO slides over means over-crimped, which can split the ring or cut into the pipe.
5. Never crimp a ring twice. A second closure deforms the ring off its designed shape, and a pass after it proves nothing. A failed ring is cut out.

  COPPER CRIMP RING ON A BARBED INSERT FITTING

        crimp ring   pipe end butted
            |        on fitting shoulder
            v          |
 ==========[##]========+
 PEX      barbs under  |###### fitting body
          the ring     |       (tee or elbow)
 ==========[##]========+
              |<------>|
     1/8 to 1/4 in, ring edge to pipe end

  GO/NO-GO GAUGE, checked twice, 90 degrees apart
    GO slot slides over ring ....... required
    GO slot will not slide over .... under-crimped
    NO-GO slot slides over ......... over-crimped

Making a stainless clamp joint

1. Same ring-then-pipe sequence, pipe butted on the shoulder.
2. Set the ring where the ring maker says, measured from the pipe end. On most systems it is the same 1/8 to 1/4 in window the copper ring uses.
3. Seat the pincer jaws over the ear, tool square, and squeeze until the ratchet releases. Stopping partway leaves a half-closed ear that reads as closed under a flashlight in a dark cabinet.
4. Check the ear against the maker's gauge or mark, and check the ring is not cocked on the pipe.
5. Same no-rework rule. A ring that fails is cut out.

A clamp ring can be rotated on the pipe before it is closed so the ear clears a stud or a drop-ear bracket, and its tool works one-handed in a tight bay. That is the field reason to carry both systems, where the pipe's print lists both.

Cutting out a failed ring

Cut the pipe off square as close behind the ring as you can, discard the fitting and the ring, and remake the joint with a new fitting. Some makers permit reusing a fitting after the ring is removed with their removal tool; that permission is theirs to give, and without it the fitting goes in the bucket.

The cut shortens the run by roughly the fitting's insertion depth plus the kerf. Where the pipe has slack in the bay, pull it through. Where it has none, the repair is a coupling, which is two more joints to gauge. And if the failed ring is on a tee, cutting it out costs the tee and the other two joints on it, so plan the remake before the cutter comes out.

Worked example: a hall bath rough-in

A hall bath remodel in 1/2 in PEX-B, metal insert fittings, the pipe printed for F1807 and F2098. The run has 14 joints: 12 copper crimp and 2 stainless clamp at the vanity drop-ear elbows, where the elbows sat tight to a stud and the crimp jaws could not close square.

7:40 a.m. Test crimp on scrap: GO slides over in both positions, NO-GO does not. Logged on the ticket.

Joints 1 to 7. All gauged in two positions, all pass.

The drop. The crimp tool fell about 6 ft off the step ladder before joint 8. The rule says recalibrate after a drop. The apprentice made joints 8 and 9 first.

Joint 9, gauge, second position: GO will not slide over. Under-crimped. The first position had passed, which is exactly the ovality the two-position check exists to find. Stop. A fresh test crimp on scrap also fails GO, so the tool, not the ring, is out. Adjusted by the maker's method; the next scrap crimp passes both positions. Logged.

Joint 8 re-gauged, since the same out-of-adjustment tool made it: passes both positions. It stays, because the gauge, not the tool's history, is the test of the ring. A tool that drifted far enough to fail joint 9 in one direction had been making marginal rings, and joint 8 sits inside the gauge in both.

Joint 9 cut out. It was the pipe side of a 90 degree elbow whose other side was not yet made, so the loss is one elbow, one ring and about 1 in of pipe. The bay had a loose loop of slack; the pipe pulled through. Remade, gauged, pass.

Joints 10 to 14, including the two clamp rings: all pass. Final count: 14 joints, 14 gauge records, one of them a remake.

Pressure test. The model codes require the water supply to be tested; the IPC 2021 test in Section 312, as adopted, is a water test at not less than the system's working pressure, and it does not offer an air test for plastic piping. The shop default here is water at 100 psi held for 15 minutes, unless the inspector or the pipe maker asks for something else. PEX stretches slightly as it pressurizes, so an early drop that stops after one re-pump is the pipe; a drop that keeps going is a leak. Filled from the lowest point, air bled at the highest stub, pumped to 100 psi. At 10 minutes the gauge read 96 psi; 100 minus 96 is 4 psi of initial settle. Re-pumped to 100 psi, then read 100 psi at the start and 100 psi at 15 minutes. Pass.

Hazard during the test: a joint that lets go at 100 psi sprays hard enough to hurt an eye, so eye protection stays on and nobody puts a face to a joint to look for a weep; look with a light and a mirror. Bleed the test to zero through the test valve before cutting, adjusting or disconnecting anything.

Restore. With the test bled off, the rough-in is opened to the house supply slowly with a faucet open downstream, and the new stubs are checked again at house pressure. The house pressure is checked against the shelf limit of not more than 80 psi static at fixtures (owned by The Pressure and Temperature Numbers on Every Residential Call), because a test that passed at 100 psi says nothing about whether the house runs too high every day.

How to verify you got this right

• The ticket carries the morning tool check and every recalibration, with times, and the gauge count equals the joint count: 14 and 14 here.
• Every ring passes in two positions, not one. Ask the tech which position failed on joint 9; if they cannot say, the two-position check did not happen.
• No ring sits on the shoulder or over the pipe end. Look along the pipe at each joint before the wall closes; the gap between ring and shoulder should be visible and even.
• The test record shows the settle, the re-pump and the hold, each as a number. "Held" without numbers is not a record.
• Photographs of every joint before insulation or drywall, so the next person who opens the wall knows what they are looking at.

References

• ASTM F1807 (metal insert fittings with copper crimp rings), ASTM F2159 (plastic insert fittings) and ASTM F2098 (stainless clamp rings), with the pipe maker's installation instructions, which are part of the listing
• IPC 2021 Section 312, as adopted, or the UPC 2021 test provisions, as adopted, for the water supply test
• See related: Reading PEX Pipe and Fitting Markings Before You Join
• See related: The Joining Method Standard SOP and PEX Installation Procedure Reference
• See related: The PEX Crimp That Let Go Behind the Vanity