There are several types of plastic plumbing pipe used in residential plumbing, but PVC has become the industry standard for drain pipes and vent lines. It is popular because it is easy to cut and fit, and because it is much less expensive than the alternatives. In older homes, main drain and vent pipes were often made of cast iron—an expensive and exceedingly difficult material to work with. For this reason, upgrades to old plumbing drain systems are almost always made of PVC pipe.
PVC stands for polyvinyl chloride, a synthetic plastic that has excellent stability and stress tolerance. Also, to drain pipes, it is also approved for cold-water supply pipes and thus is often found in outdoor irrigation systems. It does not tolerate high temperatures, though, and for this reason, it isn't used for indoor water supply systems.
How PVC Is Fitted
The process of fitting PVC together makes it easier than older materials used in pipe fitting. The pipes themselves can be cut with an ordinary saw, and a variety of convenient unions, tees, and other fittings are available to assemble a system.
The pipe and fittings are held together by a solvent-cement "glue," which essentially "melts" the top layer of plastic on both the pipe and fitting so that they merge to form air-tight, water-tight joints.
Measure PVC Pipe
When measuring for runs of PVC pipe, always measure from but the bottom of the hub on each of the adjoining fittings. This will ensure that the pipe is butted into the bottom of the fitting, maximizing the surfaces that cement together to form the seal.
Measure and mark the PVC pipe for cutting cut using a permanent marker.
Cut PVC Pipe
PVC pipe can be cut with almost any saw. Popular options are a miter saw (chop saw), reciprocating saw (sawzall), or hacksaw. You should make sure to make the cut as straight as possible to ensure a good fit. There are also hand-held, ratcheting PVC cutter tools you can use.
Clean Off Burrs
Cutting the pipe will leave burrs and flakes of plastic on the ends of the pipe. Take care to remove these off to ensure clean mating surfaces between the pipe and fittings. The burrs can usually be removed by hand, or using the edge of a putty knife or utility knife.
Drill Access Holes
Where pipe cannot be run in the cavities between studs, you may need to drill holes through studs or other framing members. Check with local building codes to determine the proper place to drill. Codes can vary from city-to-city. Never notch out a stud as this reduces its strength—always drill through the stud.
Professional plumbers often usually a specialty tool called a right angle drill to bore these holes with a hole saw bit.
Test-Fit the Pipes and Fittings
Since you will have limited time to assemble the pipes and fittings once the solvent cement is applied, it's a good idea to test fit all pieces before you begin. When the dry-fit pieces are all positioned the way you want, make a cross mark on each joint, creating a registration line that shows where each pipe and joint should align. Later, when you join the pipes and fittings, you'll be able to simply twist the pipes into position until the registration marks line up.
After test-fitting and making registration marks, disassemble the dry-fit pipes and fittings.
Prepare the PVC Pipe Surfaces
The fitting process starts by preparing the surfaces to be glued. PVC primer is a product specifically designed to clean and "etch" the smooth plastic surfaces to enhance the chemical bonding process.
Wipe the pipe and fitting down with a clean cloth, then brush the primer all around the fitting and pipe to remove all dirt and stains. Be sure to prep all surfaces being fitted.
After all fittings and pipes are clean, the assembly will proceed one joint at a time. Liberally apply a layer of solvent cement to both the outside of the pipe and the inside of the first fitting.
Join the Pipe and Fitting
After the glue is applied, push the pipe into the fitting until the end of the pipe touches the bottom of the fitting hub. Twist the pipe back and forth in the socket to spread the solvent. If you have made registration marks on the join, make sure the marks are aligned. Hold the pieces together for about 30 seconds until the bond hardens.
It is standard practice in the industry to have the lettering of the pipe facing out so it can easily be read. This will help identify the pipe size and material for the building inspector.
Level the Fittings and Pipe
Using a torpedo level, make sure the face of the fitting is straight and that the pipe at the correct pitch. Code requires horizontal runs of the drain pipe to be pitched downward 1/4 inch for each foot (or one inch for every four feet). Under no circumstance should the pipes have "back-pitch" toward the fixture drain. Back-pitching will cause future draining problems, so it is paramount that the pipes pitched slightly downward toward the main drain.
Pipe straps or blocking attached to framing members can be used to hold the drainpipe run at the proper pitch.