In this video, This Old House plumbing and heating expert Richard Trethewey shows host Kevin O’Connor how to handle sink drains in tight places.
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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.
Some Bathrooms are Tight
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.
But 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 reach out to the building department and request a variance. They must remember that they might need to inspect their bottle trap far more often than a traditional P-trap.
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From the makers of This Old House, America’s first and most trusted home improvement show, Ask This Old House answers the steady stream of home improvement questions asked by viewers across the United States. Covering topics from landscaping to electrical to HVAC and plumbing to painting and more. Ask This Old House features the experts from This Old House, including general contractor Tom Silva, plumbing and heating expert Richard Trethewey, landscape contractor Jenn Nawada, master carpenter Norm Abram, and host Kevin O’Connor. ASK This Old House helps you protect and preserve your greatest investment—your home.
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Understanding Bottle Traps | Ask This Old House