Cross-linked polyethylene (PEX) is a flexible tubing system that’s been used in Europe for radiant heating and household plumbing since the 1960s, but it wasn’t widely used in potable-water systems in North America till the late 1990s. Within 5 years, though, it had captured 7 percent of the market, even though it was unfamiliar to most plumbers and cost roughly the same as copper. Now approved by all major plumbing codes, PEX could overtake rigid copper pipe in popularity. And as PEX tubing, tools and techniques become more widespread, more and more weekend plumbers will be installing it. There’s a lot to like.
PEX Advantages
► It installs quickly. Because lengths of flexible tubing easily turn corners and snake through walls, PEX systems require far fewer connections and fittings than do other materials. PEX tubing runs to fixtures from hot — and cold-water manifolds with multiple takeoffs. Most of the fitting is simple, consisting of crimping steel or copper rings onto tubing ends. Fewer fittings also mean fewer leaks and quicker installations.
► It’s safe: No open flame, no flux, no solder, no pipe cements—in short, nothing toxic to leach into the water supplies. So there’s no funny taste. Because it’s chemically inert, PEX won’t corrode, as metal pipe will, when installed in "aggressive water conditions."
► It can take the heat. PEX can withstand water temperature up to 180°F at 100 psi, which is 40°F hotter than recommended water heater settings. And hot water will arrive faster at the tap because, unlike metal pipe, there’s minimal heat loss through conduction. Thus it’s also less likely to sweat during hot weather.
► It’s quiet. The tubing expands slightly, minimizing air hammer—the banging that takes place in rigid piping when taps are turned off suddenly and running water stops abruptly. That ability to expand also means less pronounced pressure drops (fewer scalding or freezing showers) and PEX tubing is less likely to rupture if water freezes in it.
► It’s easier to repair. Because tubing connects to an accessible manifold with a bank of lever valves, you can shut off water to one side of a fixture as simply as flipping an electrical breaker.
PEX Disadvantages
PEX is as costly as copper; you need proprietary connectors and crimping tools for each brand of tubing; and it will break down when exposed to UV light (within 30 days to 90 days), so get it installed and covered quickly. Although PEX can withstand high water temperatures, it will melt when exposed to open flame. Thus it must not be directly connected to gas- or oil-fired water heaters and must be kept away from flue pipes, recessed lights, and other sources of excessive heat.
via no-hub couplings with inner neoprene sleeves, as shown in "Splicing a Branch Drain to a Stack,” on p. 285. The new pipe-fitting assembly should be 1 in. shorter than the cutout section.
Before cutting into cast iron, however, support the pipe on both sides of the intended cut to prevent movement, which could weaken joints. Use stack clamps (riser clamps), if you’re cutting into a vertical section of pipe. Use strap hangers (see the top photo on p. 277) if cutting into a horizontal section. Mark cut-lines on the cast iron with a grease pencil. Then wrap the snap-cutter’s chain about the pipe, gradually tightening till the chain is snug and the tool’s cutting wheels align over the cut-lines. Crank the cutter’s handle to continue tightening the chain till the pipe snaps
cleanly. Make the second cut, and remove the old pipe section. Caution: Wear goggles during this operation.
Once the cuts are complete, slide the neoprene sleeve of a no-hub coupling over each remaining pipe end. You may need to roll each sleeve back on itself, as you would roll up the cuffs of a long-sleeved shirt. Insert the transition fitting or replacement pipe section, unroll the neoprene sleeves onto the fitting or pipe, and then tighten the steel band clamps. You can also tie into a cast-iron drain without cutting into it, by building out from an existing cleanout, as shown in "Extending a Cast-Iron Main Drain,” on p. 286.
