Although copper has many advantages in residential plumbing, various types of plastic piping are becoming popular. The use of cross-linked polythene, or PEX, is on the rise, especially among plumbing contractors. For the homeowner, pipe and fittings made of polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC) are both widely available in plumbing departments at home repair stores. The space in the aisles allotted to PEX is smaller. The ease and speed of installation of plastic pipe in general and PEX in particular is a major contributing factor to this increase in market share.
Working with PEX is a breeze compared with cutting, fitting and soldering copper pipe. You can run one continuous line of PEX from wherever you make the water supply connection all the way to whatever fixture you're installing. Even corners and bends can be made without any additional connectors, as long as the radius isn't too severe. That flexibility does mean more support is needed for the pipes, however. PEX requires task-specific tools as well, especially for making the all-important connections. Although approved by most plumbing codes for hot and cold water supply, the types of PEX currently available are limited in the areas they can be installed, due to a sensitivity to ultraviolet light. PEX pipe costs less per foot than copper, but the fittings can cost more.
PVC pipe is similar to copper pipe as far as installation is concerned. Because of its rigidity, you still have to measure and plan each run of pipe, taking into account the fittings you need for corners, bends and in-line connections. But instead of a torch and solder, PVC simply glues together like a plastic model. The main drawback to PVC is that it has temperature limitations. Most plumbing codes don't allow PVC for hot water supply lines. PVC pipe and fittings are much cheaper than copper.
Think of CPVC as PVC with a wider temperature range. CPVC is approved by most plumbing codes for cold and hot water supply lines. In other respects, working with CPVC is the same as PVC, except that it requires a different primer and glue. CPVC pipe and fittings are slightly more expensive than PVC.
PEX has much to recommend it as a piping material. As it gains acceptance from plumbing contractors and as manufacturers work to resolve its shortcomings, it is rapidly replacing copper in new construction and remodelling. If you plan to install PEX yourself, it would be wise to consult a professional and then be sure to follow all of the recommendations from the pipe manufacturer. PVC is nearly as common as copper for cold water lines and great for quick repairs. If you have to do both cold and hot water lines, CPVC is the better choice, and you'll have to buy only one type of primer and glue.