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Why is there a flexible accordion pipe under the sink?
Sunday, August 19, 2018
Although the flexible, accordion-shaped pipe shown in the photo above is sold in home improvement and hardware stores, it is not approved for installation by plumbing codes, which require that any waste pipe fitting to be “self-scouring,” meaning that it should have a smooth interior surface that allows the free flow of drain water and prevents waste buildup on the pipe wall that leads to clogs.
Yes, you read that correctly. Although the stuff is allowed to be sold, it is not allowed to be used, and professional plumbers do not install it. The pipe should probably have a label on it like some of the merchandise sold in adult bookstores: “ADULT NOVELTY--NOT FOR ACTUAL USE.”
We typically see it used in a sink replacement by a homeowner or handyman that has trouble aligning the drain of the new sink with the U-shaped P-trap below it. A professional plumber can adjust the length of the trap arm (the pipe running from the trap to the wall) or add an angled fitting to turn the trap arm slightly to make everything line up. Also, there is an S-shaped pipe that can used as part of the tailpiece (pipe from the bottom of the sink to the trap) to get everything aligned.
But the accordion-pipe is a quick and easy fix. Occasionally, we even see it used for a direct connection from the tailpiece to the trap arm, with the old P-trap pipe tossed in the trash. Because the standing water in the trap provides an important safety function of preventing sewer gas from rising up into the home through the sink, this is not a great idea.
Also, corrugated flexible pipes have another problem. “Sometimes funky-smelling stuff can develop in the ribs,” according to James Freeman, a local plumber. “Because it’s above the trap, it can push smelly air into the room when you run the water.”
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