Lower-Cost Plastic Plumbing Is Easy To Use

By James Dulley

October 15, 2020 4 min read

Dear James: I have never had much luck with solder copper plumbing, so I would prefer to use plastic plumbing for my house renovation. Can plastic pipe be used everywhere in the house? — Charlie D.

Dear Charlie: Copper pipe is best for the supply side of the plumbing, but plastic pipes can be used everywhere in place of copper. They are ideal for a do-it-yourself project. Typical white polyvinyl chloride, or PVC, pipe is almost always used for drain, vent and waste lines today. It is not a strong material, so it cannot be used where pipes will be under pressure.

For the hot- and cold-water supply lines that are under pressure, use rigid chlorinated polyvinyl chloride, or CPVC, plastic pipe. Check the printing on the pipe to make sure it is CPVC. In order to distinguish it from white PVC drain pipe, the CPVC pipe often is gray. Gray polybutylene pipe also is sometimes used for the supply lines.

The components of a residential plastic plumbing system can be connected by solvent welding or with mechanical fasteners and couplings. For PVC and CPVC pipes, solvent welding is usually used. It is very simple to glue the pieces together without leaks. The mechanical couplings are typically used with the flexible polybutylene pipes. Using the couplings does make it easy to remove or change things at a later time.

Solvent welding is used for many types of plastic assembly in addition to plumbing. The solvents melt the surface of the plastic, breaking down the long chemical chains. When the chains reform across the joint as the solvent evaporates, the two pieces are bonded together.

Although most pipe materials should be similar, it is a good idea to purchase it all from the same suppliers to ensure the pipe and fittings are of the same material. This also makes sure the parts fit together with the proper clearances for the strongest solvent weld joint.

Plastic piping is durable, but there can be flaws, especially near the ends. Inspect the pieces for cracks or scratches. Don't use any pieces with cracks, even if the cracks are very fine. A small scratch should fill in well enough when the solvent is applied.

It also is important for the end of the pipe to be cut off squarely so it fits completely in the fittings. If it is not, use a hacksaw or, better yet, a special plastic pipe cutter to square up the end. It sounds as though you will be doing a lot of pipe cutting, so it might be worthwhile to invest in a saw blade just for plastics.

You will find a burr around the edge of the cut pipe. Use a file or a utility knife on an angle to scrape it off. A tight fit between the outside of the pipe and the inside of the fitting is important for a good weld. Don't clean off the burr with sandpaper because you may take off more than just the burr.

Apply a primer/cleaner to the end of the pipe and to the inside of the fittings. Do not touch the surfaces after they are cleaned. Brush a coating of solvent on the end of the pipe and the inside of the fitting. Push them together; give them a slight twist; and hold them for a few seconds.

Send your questions to Here's How, 6906 Royalgreen Dr., Cincinnati, OH 45244, or visit www.dulley.com. To find out more about James Dulley and read features by other Creators Syndicate writers and cartoonists, visit the Creators Syndicate website at www.creators.com.

Photo credit: stevepb at Pixabay

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