What Is a Plumbing Drum Trap?
Plumbing traps have two basic functions: to keep sewer gases from entering a home and to catch heavy items not meant to go down drains (such as the cliche ring). The drum trap was common during the early 1900s, but was ultimately replaced by less cumbersome piping.
A drum trap looks like a miniature steel drum with an access cap at its top. Once installed, only the access cap in the floor may be visible.
Drum traps, with their large caps, make for easy access to clean clogs in drains. Once opened, a snaking tool can be inserted to seek out an obstruction.
How It Works
Water enters at the bottom of the trap, filling the trap before exiting out the top. There is always some water in the trap blocking sewer gases from escaping.
Though the drum trap is outdated, there is no reason to replace one if it is still working properly. During renovations or repairs, a plumber will replace a drum trap with a p-trap.
If opening a drum trap, make sure the source in front of it (most likely a bathtub) is empty. If not, once the trap is open, water may gush from it. If clogged, bail out the tub prior to servicing the drum trap.