Polyvinyl chloride (PVC) pipe is the most frequently used type of pipe in the installation of drinking and wastewater plumbing in the United States. PVC pipe is popular because it is inexpensive, durable, flexible and easy to work with. However, PVC pipe can crack if exposed to harsh cold or if it suffers a hard blow. If you have a section of PVC pipe in your home that cracks, then you can repair the damage yourself in most cases. Here is how to evaluate what type of pipe you have in-place, cut out a bad section, and replace it with a new piece:
Materials and tools you need
PVC pipe sections
PVC pipe couplings
PVC ratchet cutter
PVC primer and cement
Black permanent marker
How to assess your PVC pipe before repair
While PVC pipe is a simple material to handle, it comes in a variety of types and sizes that can be confusing to do-it-yourself homeowners. Broken sections need to be replaced with the same kind and same size of pipe. Here is how to evaluate your pipe to see what you have in-place:
Schedule 40 PVC – this is the standard white-colored pipe used in most installations, as it is pressure-resistant and capable of handling both cold water and wastewater. Schedule 40 PVC will be clearly marked as such.
Schedule 80 PVC – this pipe is often gray in color and it is marked as Schedule 80. It has thicker walls than Schedule 40 PVC, and though it may be seen in residential plumbing, its use is less frequent. It is also rated for cold water usage and wastewater.
Schedule 80 Chlorinated PVC (CPVC) – designed for hot water applications, Schedule 80 CPVC is strong and resistant to heat. It will be marked with its schedule designation and material type, so be sure to note the letter "C" that proceeds PVC.
PVC pipe is manufactured in various sizes that range from one-half of an inch in diameter all the way through sections that are two feet or more. In addition, PVC pipe is always measured using inside diameters; however, keep in mind that the inside diameter measurement is nominal, not actual. For example, Schedule 40 PVC pipe that is designated one-half inch in diameter is actually slightly over six-tenths of an inch in diameter. That's why it is important that you use the nominal dimensions printed on the pipe rather than any actual measurements you make.
Cutting out the bad section
Cutting PVC is not difficult, and in the confines underneath a sink or in another cramped location, a ratcheting PVC pipe cutter works well:
Turn off the water supply; usually sinks and toilets have a cut-off valve attached to the incoming water supply line. However, for fixtures lacking individual cut-off valves, such as tubs or showers, or for sections within your home in other locations, you will need to shut off the main valve instead.
It is helpful to use a bright flashlight to illuminate the pipe before cutting it to make sure you remove all of the damage. Gently flex the pipe near the crack so you can expose any nearly-invisible cracking that may extend further than you originally thought. Use a black marker to indicate where you need to cut the pipe.
Carefully align the PVC pipe cutter along the marks you made on the pipe, and press firmly until you hear the ratchet clicking. You can ease up some after the ratchet clicks each time since the cutter will be locked to the pipe, but continue applying pressure as the blade cuts into the pipe. Once the pipe is completely cut through, pull the piece away, but don't discard it yet.
Replacing the bad section
Before you install a new piece, be sure that you purchase a replacement piece in the exact diameter and schedule rating. Also, you will need to buy two PVC pipe slip couplings that enable you to insert the replacement section into the gap between the ends of the remaining pipe. PVC pipe fittings are sold in the same nominal sizes and schedule ratings as pipe, so be sure to get the appropriate couplings. Once you are ready, here is what to do:
1. Using the old section you removed as a guide, mark a new piece of pipe in the same length. You can use a black marker to mark the cut locations on your new pipe; once you do that, cut the pipe with the ratcheting cutter. Try to make both end cuts as perpendicular as possible.
2. Slip couplings on each end of your new section of pipe, and hold the assembled section up to the gap for comparison. Note that each coupling will have a small gap between the ends of the pipes once installed; the gap can vary depending on how perpendicular your cuts were made, but it will be approximately one-fourth of an inch.
3. Once you have determined how much gap is remaining on each end based on your comparison in step 2, mark and cut off that total length of pipe.
4. Apply a generous amount of PVC primer and PVC cement on the outside ends of all the pipes—the ends of the existing sections and the ends of the new section you made to bridge the gap between them.
5. Insert each end of the replacement pipe section into the couplers, and then slide the assembled section onto the existing sections. Gently flex the pipes so that the section will fit, but be careful not to break or dislodge any existing plumbing. Give the entire replacement assembly a quarter-turn twist to spread the PVC cement within the couplings.
6. Allow the PVC primer and cement to completely dry and cure before turning on the water supply; once you restore the water supply, be sure to run water through the section for several minutes to check for leaks. If the pipe supplies potable water, allow it to run freely for half an hour to flush any impurities out of the line.
For more information, or if you're rather leave the work to the professionals, you can call a local plumbing repairs company.