Plastic pipe makes some plumbing a snap

March 14, 2009|By PAT LOGAN / Creators Syndicate

Dear Pat: I am totally redoing the kitchen and bathrooms in an older house. I plan to do the plumbing myself. Because I cannot solder copper pipe, can I just use plastic pipe throughout? - Erika K.

Dear Erika: Plastic pipes can be used throughout your remodeling projects. Although it can be a somewhat time-consuming task, it definitely is a do-it-yourself job. You will need to have to use several types of plastic-pipe materials to do the entire job. For no-pressure drain-waste-vent lines, or DMW, white polyvinyl chloride, or PVC, pipe is commonly used.

Rigid chlorinated polyvinyl chloride, or CPVC, plastic pipe is used for hot- and cold-water supply lines. Check the printing on the pipe to make sure it is CPVC. Also, CPVC pipe often is beige in color instead of white to make it easier to distinguish from drainage PVC pipe. Gray polybutylene, of BU, pipe is sometimes used for the supply lines.


The components of a residential plastic plumbing system can be connect by solvent welding, or with mechanical fasteners and couplings. For PVC and CPVC pipes, solvent welding is usually used. It is simple to glue the pieces together without leaks.

Mechanical couplings are typically used with the flexible BU pipes. Using the couplings makes 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 material for sale at today's retailers should be similar, it is a good idea to purchase all your pipes and fittings from the same supplier to ensure that they are manufactured of the same material. This also ensures that the parts fit together with the proper clearances for the strongest solvent-weld joint.

Plastic piping is durable but can sometimes be flawed, especially near the ends. Inspect each piece for cracks or scratches. Avoid using pieces with even fine cracks. A small scratch should fill in well enough when the solvent is applied.

It also is important for the end of a pipe to be cut squarely so it seats completely in the fitting. If it is not cut squarely, use a hacksaw, or better yet a special plastic pipe-cutter, to square 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 might 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 cleaned surfaces. 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.

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