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About This Project
At first glance, plastic plumbing pipe looks easy to cut and join. But don’t be fooled. There’s more to a top-quality installation than meets the eye. In this article, we’ll show you some tips for cutting and joining plastic pipe that’ll guarantee a longlasting, leak-proof plumbing job.Make Square Cuts for the Strongest Joints
Square pipe ends fit snugly into the fittings, allowing plenty of contact area for the solvent cement to work. They also make a smoother interior surface for better water flow. A power miter saw and other special tube cutters guarantee square cuts, but you don’t have to buy them. You can do a good job with just a handsaw and an improvised guide. The photo shows an easy-to-use guide that’s made by screwing together scraps of 2x4.
For the best results, use a saw with fine teeth and a blade that’s 3 or 4 in. wide. A hacksaw is a poor choice because the narrow blade tends to wander easily. Special saws for cutting plastic pipe cost about $10 to $15 and are a worthwhile investment if you do much plumbing work. You’ll find them in the plumbing tool area or with the handsaws in most home centers and hardware stores. Otherwise, any finetooth saw will work.
Plastic burrs left from sawing can cause trouble. Outside the pipe they’ll interfere with a good fit. On the inside they can collect debris and slow the water flow. You can remove them with a file or pocketknife, but sandpaper is easier to use and works great. Simply roll a quarter sheet of 80-grit sandpaper into a tube and flatten it slightly to match the curve of the pipe. Then hold the sandpaper at an angle and sand the inside and outside of the plastic pipe until you create slightly beveled edges.Mark the Pipe and Fitting for Precise Orientation
By the time you spread the solvent cement on both the pipe and the fitting and press them together, you have only several seconds to get the alignment right before the pieces are stuck together. That’s why it’s a good idea to make alignment marks beforehand on joints where orientation is critical. Dry-fit the pipe and fitting, using a torpedo level if needed to align the fitting, and make a mark across the fitting and pipe. Use these marks to align the fitting and pipe when you join them with solvent cement.
Use an Even Layer of Cement and the Quarter-Turn Technique for the Strongest Joints
Just swiping the pipe with cement and pushing on the fitting won’t ensure a strong joint. You want to make sure you have an even layer of cement over all mating surfaces.
If you’re using PVC or CPVC pipe, wipe primer around the pipe and into the fitting to prepare it for the solvent cement. Let it dry about 10 seconds. Then spread an even layer of solvent cement on the same surfaces. To keep excess solvent cement from being pushed into water piping, don’t apply too much to the inside of the socket on the fitting. At this point you have to work fast to complete the assembly. Align the fitting and pipe about a quarter turn from their final orientation. Then twist the fitting a quarter turn as you press it onto the pipe.
Twisting the fitting helps spread the solvent cement evenly to ensure a solid joint. If you’ve made alignment marks (top photo), make sure they’re aligned with each other. Hold the pipe and fitting together for about 15 seconds until the cement grabs. If you let go immediately, the pipe may push out of the fitting, resulting in a weak joint.
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