PEX (Cross-Linked Polyethylene)
PEX is flexible plastic water-supply tubing that bends around corners and runs in long lengths with few fittings, now the most common material for whole-house repipes.
PEX stands for cross-linked polyethylene, a plastic tubing that arrives on a coil and flexes through wall cavities the way a garden hose does. Because it bends, a plumber can run a single line from a central manifold to a fixture with almost no joints in between, which means fewer places to leak. It comes color-coded, red for hot and blue for cold, and connects with crimp rings, clamp rings, or push-fit fittings rather than the solder and torch that copper demands.
Homeowners usually meet PEX during a repipe, a kitchen or bath remodel, or when a frozen line bursts and the plumber suggests swapping the failed run. Its big practical advantages are speed of installation and freeze tolerance: PEX can expand a little when water inside it freezes, so it survives cold snaps that would split copper. It is rated for decades of service indoors but degrades in sunlight, so it is never run exposed outdoors and is kept away from recessed-light heat and gas appliances.
There are tradeoffs. PEX cannot be used for the last stretch near some older water heaters where temperatures run high, so a short copper or CPVC nipple bridges that gap. Some homeowners dislike that it is not recyclable like copper, and a few markets still have inspectors who prefer copper on the main. For most houses, though, PEX is the default repipe material because it cuts labor hours dramatically.
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- Galvanized Pipe : Galvanized pipe is old steel water pipe coated in zinc that corrodes and clogs from the inside over decades, a common cause of low pressure and rusty water in pre-1970 homes.
- Polybutylene Pipe : Polybutylene is a gray flexible plastic supply pipe installed from the late 1970s to the mid-1990s that is prone to sudden failure and is now widely flagged by insurers and inspectors.
- Dielectric Union : A dielectric union is a coupling with a non-conductive separator that joins two different metals, such as copper and steel, to stop the galvanic corrosion that would otherwise eat the joint.
- Slip-Joint Connection : A slip-joint connection seals a drain pipe with a beveled nylon washer compressed by a hand-tightened nut, the take-apart joint used on sink traps and tailpieces.