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Plumbing • Heating • Cooling Services Sewer and Water Replacement


Plumbing Repair Question: What Does the U-Shaped Pipe Under a Sink Do?

The U-shaped pipe beneath kitchen and bathroom sinks is something that people expect to see but rarely stop to think about. “Why exactly does it have that shape? And why does it seem that every drain pipe has that same shape? It must serve a purpose, but—” And by then you’ve turned your thoughts to something more pressing.

Yes, the U-shaped construction of drainpipes serves a very important purpose, and most of the time it goes about performing it without you needing to worry about it. However, there are times with you’ll need plumbing repair because this precaution built into your sinks has encountered trouble. When you have clogs or leaks in your sinks, call Wm. Henderson Plumbing & Heating Inc. and we’ll provide you a fast and effective remedy.

The P-Trap

The U-shaped bend in your drain pipe is called the p-trap (or sometimes simply the trap, although this can refer to a number of plumbing fixtures that serve similar purposes). The name refers to the shape when viewed at an angle, as there was already a similar fixture called a U-bend.

The p-trap serves the function of capturing a small amount of water inside your drainpipes after the sink is used. This plug prevents sewer gases from coming up the wastewater line and out the sink. It also can trap small objects that fall down the sink, such as jewelry, making it easier to extract them. (Many modern sinks have a valve along the bottom of the p-trap to allow easy access to anything that might have fallen into them.)

P-traps can become trouble spots in some cases. Because they trap water, they can also trap debris inside the water, such as hair and soap scum, and this can eventually cause the p-trap to clog. A plunger might remove the clog, but if it can’t, you’ll probably need a plumber to come out to clear it using a drain snake, hydro-jetter, or by completely removing the p-trap.

The other common trouble with p-traps is when they dry up. If a sink doesn’t see frequent use, the water in the p-trap will evaporate and sewer odors will begin to escape from the drain. If you detect foul odors from around a sink, try running water through it to fill up the p-trap.

The p-trap will quietly do its job for you until something goes wrong with it—and then you’ll need expert plumbers to help. For the plumbing repair to keep your drains running, contact Wm. Henderson Plumbing & Heating Inc.

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