How to Use CPVC Plastic Plumbing Pipe

Easy to cut and join, no special tools, no risky soldering

CPVC: Materials and tools

CPVC tubing and fittings are perfect for areas of the country that have aggressive water that eats away at copper pipes. This aggressive water can sometimes eat through copper pipe within eight years. CPVC is unaffected by aggressive water, and its smooth inner surface won't collect mineral deposits. It's also less expensive than copper.

This system is designed to be very user-friendly, and because the outside diameter of CPVC tubing is sized the same as copper pipe, the grip-style mechanical fittings (Photos 3 and 4) can be used on both copper and CPVC. Don't confuse CPVC with the plastic polybutylene systems that were a problem more than a decade ago. Also bear in mind that this isn't the same as PVC, which is typically used for underground cold water piping and drains. You can quickly distinguish between the light beige color of CPVC and the bright white of PVC. If you're not sure, look for the printing on the side of the pipe. CPVC tubing is available at home centers and hardware stores in 1/2-in. and 3/4-in. diameters in 10-ft. lengths.

Are there any drawbacks to CPVC?
You may have heard claims about CPVC and chemical leaching, the transfer of chemicals from the pipe into the water. Studies have proved that CPVC tubing and fittings are completely safe for home water supplies. In fact, CPVC has been successfully used in homes for more than 35 years. Be aware that many home copper or steel water pipe systems are used as grounding for electrical wiring. CPVC is not a good conductor, so changing to it may change your grounding system. Check with an electrician if you think you've broken the continuity of your electrical grounding.

CPVC is not as tough as copper or galvanized steel. Take care not to strike it with a hammer, and be sure to use steel nail plates in wall framing if a nail or screw puncture is a possibility. Because of its flexibility (which can be an asset), you'll need to support it more often than copper or galvanized steel—every 32 to 36 in.

CPVC is code compliant—almost everywhere. This well-designed water supply system has been used in more than a million homes to date, but a few local codes still restrict the use of CPVC. CPVC is capable of carrying 180-degree water at 100 psi (water in the average home is about 125 degrees at 50 psi). Contact your local plumbing inspector to see if CPVC is permitted in your area. Note: Never use CPVC for compressed airlines. It may rupture from the pressure.

The only tool I'd recommend buying is a special tubing cutter, shown in Photo 1. This type of cutter is designed to produce straight, burr-free cuts on CPVC and PVC tubing. You can also cut this pipe with an ordinary fine-tooth saw, but deburr the cut end with a pocketknife, file or sandpaper (See below). This step is absolutely necessary to get a good mechanical (Photo 4) or glued (Photos 5 and 6) connection.

Figure A: Chamfered Tube Edge

After cutting, ease the outer tubing edge with a file or sandpaper to deburr it. This makes joining easier.

CPVC with chamfered edge

How to make connections

If you've ever done any soldering, you know that you have to get rid of all the water in the adjacent copper pipes to heat the pipe to accept the solder. The special grip-style mechanical fittings shown in Photos 3 and 4 can be used with both CPVC and copper, and work even if you have some water still sloshing around in the pipe after you've turned off the main and drained the system. These grip-style fittings are much easier to install in situations where pipe condensation would make soldering a real chore.

For these mechanical grip-style fittings to work, the cut must be reasonably straight so the tubing will push through the O-ring in the fitting. The fittings have a one-way gripper ring that grabs the pipe as you push it into the fitting; it's like one of those Chinese finger puzzles you played with as a kid. Once you lubricate the end of the tubing with a drop of dishwashing liquid and push it into the fitting, it won't come out.

The next step is to tighten the nut (be sure it's backed off at least one or two turns from tight before you push the tubing into the connector). As you tighten it, the tubing is pushed inside the O-ring. You'll feel some resistance as you slide the tubing past the gripper ring and then more resistance when the tubing slides into the O-ring. Don't use a wrench to tighten the nut. Just hand-tighten the nuts on all fittings of this type. A wrench may damage the fitting.

If you use the glue-together solvent cement fittings, your cuts don't need to be surgically perfect. Just cut the tubing with a tubing cutter or a fine-tooth hacksaw or wood saw, remove the burrs and you're ready to go. The joint gets most of its strength from the slight taper on the inside of each fitting, so a reasonably straight cut is necessary for a good fit.

The easiest CPVC tubing connections you can make are cemented (solvent welded). Be sure to remove the burrs and lightly chamfer the end of the tubing. Keep in mind that a crooked cut will have less surface area to cement and a greater chance to leak. The cement-on tees, elbows and couplings are considerably cheaper and simpler to use than the mechanical fittings, and because of their small size, fit nicely into tight areas. Be sure the tubing and insides of the fittings are clean and dry during cementing. Some codes require a primer (the purple product shown in the photos). Spread the cement lightly on the inside of the fitting and a bit heavier on the pipe. Go around the tubing several times with the dauber (Photo 6) to work the solvent into the plastic. Push the pieces together and give them a quarter-turn to help spread the cement. Wait at least an hour (longer in unheated areas) before checking for leaks.

Plan for tube movement

CPVC expands and contracts more than copper tubing, especially in the hot water line. A 10-ft. piece of tubing can grow in length by as much as 1/2 in. Never butt the tubing against a framing member. Leave a gap, as shown in Photo 8, especially in a long run. Runs longer than 30 ft. require a U-shaped detour about 1 ft. on a side somewhere in the length to allow for expansion and contraction.

When drilling holes through framing members, you'll also need to give the piping some space (Photo 9) to allow the longer horizontal and vertical tubing to move.

Other special CPVC parts

In our photo series, we show you how to run the hot and cold water supply lines to a basic half bath (sink and toilet). Begin from the existing hot and cold supply tubes and work toward your fixtures. We show a CPVC-copper connection. If you need to connect to galvanized pipe, use a special threaded connector with a built-in seal exactly like the female CPVC fitting shown in Photo 14. You no doubt noticed those odd, bulb-shaped items attached to the hot and cold water supply lines shown in Photo 13. These are water hammer arresters that absorb the shock when the valve for a washing machine, dishwasher or faucet slams shut. Homes without these devices often have banging pipes. Water hammer arresters, or mufflers, stop banging pipes and prevent faucet or pipe damage. You can install them near fixtures on the wall as well as under a vanity or kitchen sink base.

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