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Plumbing and heating expert Richard Trethewey shows host Kevin O’Connor the options for plumbing a drain to a low-profile sink. These sinks stand out half the distance of standard models, so Richard explains how a bottle trap may be the only choice for the job. The problem? They’re illegal, and he explains why.

Half-baths are extremely convenient. They can fit in tight places and give the home an extra powder room for guests. However, they’re often very small and require compact, low-profile lavatory sinks, and plumbing the drain becomes an issue. P-traps are typically too long, and tweaking them around never looks right. But who needs a trap, right?

We all do.

Traps Are Required by Code

All sink drains need to have traps. The traps catch water, and that water holds back dangerous and smelly sewer gasses. As water runs down the drain, it collects in the bottom of the trap, successfully blocking any gasses from passing through.

But what if a trap won’t fit? A bottle trap almost always will.

Bottle Traps Are Great for Tight Spaces

Bottle traps, also called decorative lav traps, are small, compact, and clean-looking drains that fit in tight places. They look similar to a chrome baby’s bottle, and on the inside, there is a pipe that allows drain water to flow by without draining completely. It’s this half-filled pipe that blocks the gasses from passing through.

There’s one problem: They’re illegal.

Bottle Traps Aren’t Code-Compliant

Bottle traps aren’t code-compliant with modern building codes. Modern code doesn’t allow for a pipe within the trap (also known as an internal partition), as if it cracks or fails, the homeowner won’t be able to see it, and sewer gas may pass by.

Also, drain traps need to be passable with a mechanical device like a snake. Bottle traps don’t allow a mechanical device to pass through, so they don’t meet that aspect of the code, either.

Finally, traps need to be self-scouring, meaning that they clean themselves as water passes through. Again, bottle traps don’t meet this particular requirement either.

Bottle Traps May Be the Only Answer

While bottle traps aren’t legal, they may be the only answer. When this is the case, the homeowner or contractor can request a variance from the building department. They must remember that they might need to inspect their bottle trap far more often than a traditional P-trap.