Should a home be plumbed in CPVC or PEX?

There has been a long standing debate surrounding CPVC versus PEX piping for residential applications.  Both chlorinated polyvinyl chloride (CPVC) and Crosslinked polyethylene PEX) piping are used in residential plumbing systems throughout Arizona, although PEX has the larger market share by a fairly wide margin. Still, we encounter CPVC fairly often in the course of providing plumbing repair and service to homes in the Phoenix metro area.

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Stevens Plumbing Phoenix AZ cpvc versus pexThere was a leak in this CPVC pipe.

The picture (left) is of a section of CPVC piping installed in a Phoenix home. The pipe was leaking, and the homeowner called us out to find and fix the water leak.  In this particular case, the CPVC had been installed improperly; the pipes were installed too close to the drywall and a nail had been driven through the pipe.  Over time a leak developed at that location.  Since the home was relatively new, and the rest of the water piping was in decent condition, we simply cut out and replaced that section of piping with a new piece of CPVC and fittings, and the home was back in order in no time (see picture of repair, lower right).

There are many reasons why CPVC pipe can leak.

Unfortunately, there’s a good chance that this homeowner will have more problems with his plumbing system in the future. CPVC has certain qualities that make us, as plumbing professionals, consider it a poor choice for homes in the Phoenix area.

For several reasons, we prefer PEX over CPVC.

CPVC does not hold up well in extreme heat.

The most important consideration is how CPVC reacts to temperature extremes. Of course, in the Phoenix metro area the first thought when talking about temperature extremes is probably the hot, hot summer temperatures. And, without a doubt, heat this extreme is very troublesome when you’re talking a vinyl product (chlorinated polyvinyl chloride/CPVC). Anything constructed of vinyl, including CPVC, can become brittle and the integrity of the material can degrade over time with exposure to high temperatures. In the case of CPVC plumbing pipes, this degrading of the pipes ultimately can lead to cracks and water leaks.

cpvc repair at Phoenix homeThe glue used in CPVC joints can also be a problem.

Another worrisome issue with CPVC is that the fittings are glued together, and the glue does not hold up well against heat. In time, the glue may dry and the fittings can then loosen, resulting in leaks at the joints. Since a CPVC plumbing system requires many more fittings than a PEX plumbing system, with CPVC there are many more weak points that can potentially result in water leaks in your home.

Even cold temperatures can cause problems with CPVC pipe.

Heat is not the only enemy CPVC has.  Phoenix is known as the “Valley of the Sun”, and millions of people come to the valley to enjoy our relatively mild winters. Yet it’s a fact that we do experience cold – even sub-freezing – temperatures during the winter months. And CPVC can split fairly quickly in a freeze. Where CPVC is installed in the exterior walls and/or the attic of a home, if these walls have an exposure to extremes of temperature – such as a west wall might have in the summer, or a north wall in the winter, or if the pipes are installed in an attic but not insulated – problems caused by exposure to extremes of heat or cold can, and do, occur with CPVC piping.

CPVC versus PEX.

PEX piping, on the other hand, is a much more flexible product and much more resistant to temperature extremes. It does not become brittle in the heat, and is not as susceptible to splitting in a freeze. And, not only does PEX require fewer fittings during installation, those fittings are joined with a special tool that ensures a more reliable fitting, with no glue that can dry and loosen.

Finally, PEX pipes can safely be air pressure tested before any water is released back into the plumbing system. Potential problems can be proactively located and fixed with no potential for water leaks. Manufacturers of CPVC, however, do not recommend air testing because the brittleness of the product leaves it vulnerable to a dangerous explosion unless air testing is done with very low pressure – pressure too low to expose possible leaks – therefore the plumber can only wait until a water leak shows up to resolve any problems with your CPVC system.

If you have questions or would like to talk with an experienced plumber about CPVC pipe, or PEX pipe, give us a call.  An experienced plumber is always available to talk with you during business hours.

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