PEX is an abbreviation for polyethylene with cross-links, a new type of tubing used in residential plumbing systems. It is considered a viable alternative to older PVC, CPVC and copper “water pipes”, ranging in size from 1/4 inch to 4 inches.
It comes in white, although it's more common to see red and blue PEX tubing, where red carries hot water and blue PEX carries cold water.
PEX Tubing vs Copper Pipes
Installing PEX tubing takes less time than copper pipes, because fewer connections are needed and there's no soldering required. PEX connections are made by pushing 2 matching parts together with a compression fitting, or by using an adjustable wrench or crimping tool.
It is possible to merge PEX tubing with existing copper and PVC systems with special fittings to join a copper pipe on one end, with PEX tubing on the other end. These fittings also allow the diameter of the pipes to expand or be reduced in size.
Benefits of PEX Tubing
The benefits of using PEX tubing for plumbing include:
- Flexibility – allows the tubing to bend in a wide arc where space permits, or to make sharp turns using elbow joints.
- Direct routing of pipes – PEX is able to run straight from a distribution point to a fixture without cutting or splicing the pipe, reducing or eliminating the need for costly joints.
- Greater water pressure at fixtures – With fewer sharp turns, water pressure at sinks, showers and toilets is higher.
- Lower materials cost – With copper prices rising dramatically, PEX offers a much lower cost for plumbing installation. PRX fittings though, cost more than copper but you need fewer of them.
- Reliable – PEX doesn't corrode or develop pinhole leaks.
- Less likely to burst from freezing – PEX pipes are slower to burst than copper or PVC pipes, but they will eventually burst when freezing water expands. Some believe PEX pipes can freeze and thaw 5 or 6 times before they split, while copper will split on the first freeze and PVC shatters.
PEX tubing cannot be used in areas exposed to sunlight because it degrades fairly rapidly, so watch where you store these materials before installation. PEX is also vulnerable to being perforated by some plant-feeding insects.
A great resource on PEX tubing is the Design Guide: Residential PEX Water Supply Plumbing Systems.