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Making Joints

Every PEX manufacturer supplies fittings to go with its tubing. Naturally, if you’re using a company’s tubing, they want you to use their fittings, too — no company recommends mixing brands of tubing and fittings. The different methods of making joints vary quite a bit. Wirsbo’s basic joint for residential plumbing is a simple expansion joint, based on the tubing’s "memory," or tendency to return to its original shape whenever it’s deformed. To make the joint, you expand the tube with a special Wirsbo insert tool and quickly slide the expanded tube over the nipple of the fitting. In a split second, the tube shrinks and grabs the fitting (Figure 3).

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Figure 3. To make a simple joint using Wirsbo's method, you slide a PEX ring over the tube, expand the tube with Wirsbo's expanding tool (left), and quickly insert the fitting (right) before the PEX returns to its original diameter. You have to move fast to slip in the fitting, and once the joint’s together, you can’t pull it apart. For added strength, you slip a second ring of PEX over the tube before expanding it. After 30 minutes, the joint can be pressure-tested to 200 psi. I prefer the crimp fittings supplied by Vanguard, because they’re easier to use. With this fitting, the tube doesn’t have to be expanded: The male end of the fitting slides into the tube easily. You use a special crimping tool supplied by Vanguard to crimp a copper ring over the joint (Figure 4).

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Figure 4. In the Vanguard joint system, tubing slides over the fitting without expanding (left) and is secured with a copper crimp ring. Crimping with Vanguard’s crimping tool takes only a few seconds (right). Unlike the expansion joints, which are permanent right away, crimp joints can be pulled apart until the ring is actually crimped. This allows us to make a temporary joint at the end of a line, using a fitting that doesn’t belong there, until we come back with the correct part. However, you can get in trouble leaving joints assembled but uncrimped. Sometimes it seems quicker to make a bunch of joints, then go back and crimp them all at once. But you’d better not forget one, or you’ll have a leak. Vanguard supplies a go/no-go gauge for checking joints to make sure they’re properly crimped. If the gauge slips over the ring, it’s a go. But Vanguard’s new crimp rings also have a black coating that gets scraped off when the ring is crimped — if the ring’s still black, you know it hasn’t been crimped. However, you still have to routinely check the crimped joints with the gauge to make sure your crimping tool is properly calibrated. A third type of joint, which uses a compression fitting, comes as standard issue on manifolds (and the valves I use in making my own manifolds). To make these joints, you simply slide the tubing over the nipple, then tighten down a locknut that pushes a compression ring over the tubing. Depending on the tube’s inside diameter and the fitting size, you may have to expand the tube first. When these joints are only finger-tight, they can be backed out; but once you tighten them with a wrench, they’ll never come loose. For added security, though, we use a thread lock like Loctite to make sure the nuts don’t work off. The mother of all joints is a compression-ring fitting system supplied by Rehau. To make those connections, you expand the tube and slip it over the fitting, then use a foot-operated hydraulic press to force a heavy-duty brass ring over the tube and fitting (Figure 5).

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Figure 5. Rehau’s joint method uses a foot-operated hydraulic press to force a heavy-duty brass ring over the tube and fitting. The author rarely uses these heavy-duty joints in residential work.