How To Look At A House
McGarry and Madsen's home inspection blog for buyers of
site-built, mobile/manfuactured and modular homes
What is a drum trap at a plumbing drain?
Tuesday, July 2, 2019
A drum trap is one of several types of plumbing traps that were once acceptable, but now prohibited. The primary problem with a drum trap is that it is not “self-scouring,” per the requirement of Florida Plumbing Code (FPC-1002.2) and a similar citation in the International Plumbing Code (IPC). The drum shape creates pockets that will trap debris and grow bacteria.
Here’s a full list of prohibited traps from FPC-1002.3.
The exception, which allows use of a drum trap for situations where a “solids interceptor” is needed, is helpful at a dental office so any crown, filling, or such can be retrieved from the drum if accidentally dropped down the drain. So the lack of a self-scouring property becomes an asset. The drum is openable for cleaning.
The drum trap shown at the top of the page is a little unusual because it is a both a drum trap and an S-trap combined, and has what would be an excessive trap seal by today’s standards. The diagram above shows the more common type. But, if found in a residence today, a drum trap is an antique leftover from a bygone era.
To learn about the bottle trap, another prohibited trap that looks similar but is a slightly different configuration, and often comes attached to a “designer European” sink fixture, see our blog post Why is the European-style bottle trap not approved by the plumbing codes in the U.S.?
For other prohibited trap designs, see our blog post What plumbing traps are illegal by code? Also, see our blog posts Can I make a trap under the sink from straight pipe and 90º elbows? and What is an "S-Trap" under my sink? Why is it a problem?
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Here’s links to a collection of our other blog posts about PLUMBING:
Photo - Ryan Fessler, Diagram - Carson Dunlop
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