Plastic Pipes Used in Plumbing
A Brief Overview of a Wide Variety of Pipes and Tubes
Before a homeowner attempts to do any home plumbing, it is important that they know exactly which type of pipes or tubes to use, as they all serve different purposes.
It seems obvious, but it should be stated for the sake of being thorough: not all pipes are created equal.
That’s step one to understanding how plumbing works and how to know which products are best for which jobs. This is important to always remember because while some pipes are obviously different from each other and not at all easily confused (galvanized water pipe versus six-inch perforated PVC drain pipe, for example), but there are some pipes that are easily confused, and easily misused. That is why it is important to have at least a basic overview of the different kinds of pipe available (at least, the most important ones – some of the more obscure pipes will surely be skipped for now) before deciding which one to buy for a given project.
PVC vs. CPVC
PVC stands for Polyvinyl Chloride (though this is not important to remember at the hardware store). It is used as a standard, high pressure water pipe throughout many homes. PVC comes in multiple thicknesses, though the most commonly used in home water systems is known as “Schedule 40,” which is denoted by its thick walls and white color. There is also a slightly stronger version known as “Schedule 80” which is normally gray in color (and is fully compatible in terms of sizing with schedule 40) and a lighter, thinner version sometimes referred to as “thin wall.”
Standard PVC pipe (which ranges in standard size from ½” to about 4”, generally) is meant to be used for cold water applications only. It is not formulated to stand up to hot water.
For hot water, it’s best to go with…
CPVC
CPVC stands for Chlorinated Polyvinyl Chloride (that extra chlorination makes all the difference), and is distinctive for its yellowish color. This plastic pipe is somewhat flexible and has thinner walls than standard PVC, though is more resistant to heat, and works well for hot water supply applications. CPVC is beneficial also in that it possesses the same outer diameter (O.D.) as Type L copper, so certain fittings, such as compression fittings and “Sharkbite” fittings can be made to adapt one type of pipe from the other.
The same can also be said for…
PEX
One of the newer materials on the market, PEX pipe has actually been around since the 1920’s, but has only recently been gaining steam in home use. PEX is a nearly universal, flexible tubing which comes in either a standard “milky white” color, or distinctive red and blue (denoting hot and cold) colors. PEX will work with any temperature of water in the home, and shares the same O.D. with both CPVC and Copper so that it can be used to replace either of these pipes (and usually with far less cost).
Because of its high resistance to heat, PEX is often used for hydronic (water-based) in-floor heating systems in new homes.
There is a wide variety of ways to connect PEX pipe, as well. Professional plumbers often use connections that are permanently crimped onto the pipe using a special tool (some states require a special license in order to use this method). Other, far simpler fittings exist as well, though, ranging from “barbed” insert fittings that work in tandem with hose clamps, or very simple “push fit” fittings such as “Sharkbite” or “Watts” fittings that simply slide onto the pipe and seal with an O-Ring. These latter fittings are also beneficial because they can be removed and the pipe can be reused.
PolyPipe
That thick, somewhat rigid, black pipe that leads from the water meter box to the house (this is a generalization, of course – there are many different setups depending on where the home is located) is known as PolyPipe. It is a very durable, high pressure tubing used to carry the main source of water from the main line to the home. This pipe is generally only used for this outdoor purpose, and is buried sufficiently deep underground to avoid freezing during the winter (different locations have different codes as to how deep this must be).
PolyPipe is joined together, usually, with either plastic, steel or brass barbed fittings, which are jammed tightly into the end and then tightened even further with hose clamps (two hose clamps per end are recommended).
Those, in essence, are the basic forms of plastic pipe commonly used in standard home plumbing (though drain pipes, such as corrugated and thin-walled PVC were skipped over for the sake of brevity). With a decent knowledge of these, as well as a brief overview of their metal counterparts, the average homeowner will be well-equipped to make a decision as to which pipe is right for them.
