Q. On the topic of copper water pipes, which you addressed in a recent column, I have related questions. My house, built 20 years ago had polybutylene blue plastic pipe leading from the street and also within the house. Since blue pipe is known to suddenly break, I recently had the exterior pipe replaced with copper. The house is built on a slab with the current plumbing running the length of the house underneath. The proposal for the interior would run the pipes through the attic, tucked under the insulation so they would not freeze. However, as you have indicated, the use of copper risks pinhole leaks and, thus, ceiling problems. Is the attic plumbing a good idea? Should I ask for something other than copper, or specify a certain grade of copper? What would be the difference in cost?

The water enters the house at the laundry and kitchen but the water heater is upstairs at the opposite end over the bathrooms. The new plumbing would still return hot water the length of the house with a nuisance lag time for dishwashing. I seldom use hot water for laundry. Would it be economically practical to install another heater in the attic over the kitchen? What about a tankless one?

A. The problem with polybutylene plumbing pipes has plagued homeowners since the mid-1970s when it was introduced. I have heard of some failures where the homeowner heard a sudden bang then water started flowing from all sorts of places. There has been lots of finger pointing as to the root causes and one of the largest class action lawsuits resulted from it. The Consumer Plumbing Recovery Center (1-800-356-3496) oversees the distribution of what’s left of some $750 million dollars awarded. The base requirements as I understand them are that you have to have had two qualified leaks within a year and that year had to have been with thirteen years of the original installation. You don’t qualify because in twenty years you haven’t had a leak and that’s what I’d like to focus upon for a minute.

Polybutylene pipe was installed using a system of fitted connectors, usually copper, with a crimp-ring to hold the pipe onto the fitting. Plumbers liked the system because it was easy to install—about $600 cheaper than traditional copper—and because you had to have a special crimping tool to install the joints, amateurs and homeowners couldn’t work on the systems themselves building a sort of job security into the program for the installing plumbers.

Looking over the history of the reported leaks it becomes clear that nearly ninety percent occurred at the joints. That throws the calibration of the tool or the workmanship of the user into question. Of the remaining leaks, all of which were seemingly spontaneous, some researchers have blamed the disinfecting chlorines in the public water supply for attacking the plastic. I can’t remember where I heard it and I was unable to locate it in the literature but I distinctly remember the number of two parts per million of chlorine in the water as being the level that became problematic for the plastic.

If I had 20 year-old polybutylene pipes in house on a slab that hadn’t previously given me any trouble, I be hard pressed to pre-emptorily replace them but that’s a personal choice and I respect that. No one can guarantee that they won’t leak and no one can predict that they will.

I don’t like plumbing pipes up in the attic and would work as hard as I could to hide them anywhere but in the attic. I’ve run them along a ceiling and wall connection and covered them with bulkheads and crown molding to avoid the attic. Also I’d use cpvc plastic (no leak history) water lines. They will be cheaper to install and you won’t have someone with an open flame sweating solder joints on copper pipe around dry wood framing. However, if you have your heart set on copper use the harder Type L copper pipe, rather than the lighter Type M. Then you won’t lose sleep worrying about pinhole leaks.

As for the cold dishwater, consider a small office-style water heater that might fit under a cabinet or in the lower level of a pantry close to the sink to give enough hot water to do the dishes. An on-demand tankless water heater would require a big wiring retrofit to get enough power to the unit to supply it and the heaters themselves aren’t cheap.