Q. No-hub rubber couplings with band clamps on the ends are handy for making all sorts of plumbing connections, but are there limitations on where they can be used?

A.Mike Casey, a licensed plumbing contractor and co-author of Code Check Plumbing, responds: Often referred to as Fernco fittings (after the name of a major manufacturer), flexible neoprene and elastomeric PVC couplings are available in dozens of sizes and configurations. They’re designed for nonpressure (drain, waste, and vent) applications, and are manufactured in shielded (completely wrapped in stainless steel) and unshielded (stainless band clamps at each end only) versions. They’re accepted by a number of codes — including the Uniform Plumbing Code and the International Plumbing Code — for both above- and below-grade use.

I’ve installed many of these couplings above and below grade and have never encountered a problem. Be aware, however, that the listings for some of the couplings indicate that use above grade is subject to approval by the local building official. Always use the correct coupling for the pipes you’re connecting, and check with your inspector when the coupling is used above grade.