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The Problem With Flex Drains

Yes, the flexible accordion-style sink drains / waste pipe are sold at the local hardware stores. That doesn’t mean that they are a good idea to install under your bathroom sink.

Flexible pipes are not code compliant because they collect dirt and grime that's supposed to flow down the drain. The zigzag sides make it easy for water slow-down, which results in more gunk collecting further along toward your home’s plumbing system.  Code requires smooth drain surfaces so that water flows without restriction.

They have a tendency to clog at a much greater rate than smooth-walled pipe. Plumbing standards today require a smooth-walled pipe capable of self-cleaning to be used for sink drains and waste pipes. What is self-cleaning? The swirling action of the water going down the pipe creates enough friction to “clean” the interior of the waste pipe, at least in theory.

When you install a corrugated flexible drain line in place of a more rigid tailpipe, you now break up that swirling motion and the pipe will no longer clean itself. Furthermore, the indents of the pipe are significantly more likely to catch debris, grime and other nastiness, further reducing the flow of the waste water. Think of things like hair and makeup that has been washed down the drain collecting in those grooves.

The third reason most flexible drain lines are bad is that it is indicative of poor workmanship or at the bare minimum, someone who lacked the skill needed to line up two reasonably flexible and thin-walled plastic pipes to drain appropriately. Good plumbers don’t need to use flexible drain pipes in a vast majority of circumstances. There are situations where the flexible drains are basically the only thing that will fit in place, but these are exceptions.

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