Plumbing Traps: Simple…right?


By Douglas J. Burgasser, P.E., Warren Engineering

A plumbing trap is a simple but important device. Its purpose is to retain water in the drain pipe so that sewer gases do not escape (back-up) into the living space. It is nothing more than a “U” shaped drain pipe that is installed beneath each sink, bathtub, shower, etc.

Pretty simple right? So why would we bother to write an article focusing on such a simple device? Well, no need to include a long narrative on this subject. Instead, the following actual photos taken during home inspections will show you clearly how a simple device can be applied incorrectly: 



Here we have a common, properly installed trap. Now look at these photos: Of course, not installing a trap is a bad idea.



But if one trap is adequate, two must be better, right?



And if two are good, why not three?



A sideways trap won’t be as effective.



And while we’re at it, when installing a trap, do NOT use tape OR flex pipe!  When in doubt, call a plumber.



A simple device like a plumbing drain trap can be applied poorly, over-applied and patched temporarily. We see it every day. Although the pictures above can be considered humorous, a leaking drain can also cause significant damage in a home. Reliable plumbing in the home starts with proper installation.



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