By Murray Corporation on Mar 12, 2019 9:28:00 AM
PEX (cross-linked polyethylene) is an increasingly popular material for plumbing applications. It is most often used domestically, for potable water and radiant heating.
It offers numerous benefits, the most important that it’s significantly less expensive than copper, at about a quarter of the cost. It’s also easier to work with, since installation involves neither the soldering needed for connecting copper pipes nor the gluing needed for PVC.
Of course, installing PEX pipes still involves expertise and a special tool. The specialized clamps used with PEX piping have been designed to provide tight, secure seals, but that’s only possible if you use the right pinch clamp tool.
Making The Right PEX Connections
A PEX clamp’s tongue-and-groove design provides a smooth, circular surface around the entire pipe. The installer crimps a protruding ear, generating a uniform clamp force around the pipe’s circumference. This design prevents the leak path that you can get when you use a worm drive or similar clamp, which has a flat section where the clamp is tightened.
To ensure the best seal, you need to crimp the ear fully. This requires a high degree of force, given the sturdy materials of the clamp. ASTM requirements call for the use of a specialized ratchet crimper that multiplies the amount of force that you apply.
That specialized crimper has a special “one-way” design. Once you start closing down on the ear, you can’t open the jaws again until the crimp has been completed. This ensures that all of your seals are done properly.
The other way the tool ensures an optimal seal is that it gathers only the proper amount of metal in the ear. If you have the wrong amount of material, the clamp can be under-crimped, leaving a loose seal, or over-crimped, cutting the ear immediately or leaving a crease that can break later. Using the right tool avoids all of these possible problems.
Because the ear (and not the clamp itself) is fastened with the tool, you only need one crimper, regardless of the sizes of the pipes you install. With the compression tools you use installing copper piping, you need one for every pipe size. With PEX pipe installations, once you acquire a single crimping tool, you’re set.
Avoiding Clamping Mistakes
You may be tempted to avoid getting that tool, and just grab a cutting tool. It looks similar to the pinch clamp tool, and can provide a tighter seal. Don’t use the cutting tool, though. Since it’s designed to cut, it will either cut the ear when it’s installed, or create scoring that will cause the seal to fail later. Close-up photos of seals created by the two tools reveal the different results you get with the two types of tools.
You also need to be careful not to crimp too fast. Cold flow isn’t just an issue over time: it affects the seal in the few seconds it takes to apply a pinch clamp. The stiff material of PEX piping actually gives a little as the clamp is applied. If you don’t allow time for that to happen, the seal you create won’t be as tight as possible.
At moderate temperatures, you should take about two seconds to complete the crimp; at colder temperatures, you should take three seconds. With the right clamps, you can complete installation in near-freezing temperatures, so check the clamp’s specs: Inferior clamps will either leak or fail if installed in low-temperature conditions.
In addition, the two- to three-second speed means that you should use a manual tool to install crimp clamps. Pneumatic tools may be easier on your hands, but they’re just too fast to allow cold flow to take place. The band will overstretch, leading to seal failure.
One Final Tip For Success
Make sure the clamp is at the right distance from the end of the pipe. If you place the clamp too far from the end of the pipe – or too close to it – you won’t get a tight seal. Instead, check that the clamp is placed properly over the fitting that you’re attaching the pipe to, so you’re actually sealing the pipe snugly to the fitting.
Choose The Right Clamp For Your Application