When pipes in cement go bad

Q. I have a question regarding a possible future problem that my neighbors have had. We live in the same ranch-style house, built on a slab with plumbing and heating pipes encased in the cement floor. These houses are now 60 years old, and the bottom of many waste pipes have rotted out and had to be replaced. That means tearing up the cement floor, a real messy job. I read about a company that uses a camera and sprays liquid plastic inside the walls of the waste pipes. When it hardens, we now have a new waste pipe without ripping up the cement floor. Have you heard of this? Does it work?

A. Yes, I’ve heard of this process and have even written about the procedure in two previous columns, referring to pipe sleeves and the dangers of plastic piping in fresh-water supply pipes, and touting the ingenuity of the technology. It’s not a perfect solution, since the pipe lining becomes the new pipe within a pipe, slightly smaller than the older outside pipe, and it has to be smoothly applied so as not to hinder flow in the pipe. The waste pipe has to be accessible for the size of the equipment inserted into it, so you may need to protect the area around where the work is going to be done at the mouth of the pipe access. In the future, the equipment will be smaller and require less area to perform the process. There are also varying types of materials, from “food grade” to polymers with more toxicity, which is part of what I wrote about last.