What Is The U-Shaped Pipe Under My Sink?

Ever wondered why your drain pipe below the kitchen and bathroom sink doesn’t just go straight down into the floor, or why it has a U-shape? That section of your drainpipe is known as a trap, and it’s a critical part of your wastewater disposal system. Without it, sewer gasses would come right back up through your sink drains and waft through your house.

The plumbing trap has two major purposes:

Purpose 1: To prevent sewer gasses from entering your living space. 

The pipe bend known as the trap ensures a water seal separates the sewage system from the inside of your home. Like the rest of the wastewater system, it relies on gravity to keep the water within the bend. 

Whether you have a septic tank or a municipal waste management system, the organic waste creates fumes and gasses that can be foul-smelling and dangerous if they enter your home. If the goal of the wastewater aspect of your plumbing is to isolate the organic waste from the home residents, then the trap below the sink is a vital aspect of that.

Purpose 2: To prevent foreign objects from blocking up your entire plumbing system. 

Imagine that your sink drain on the second floor of your home was a straight shot down to ground level. If you’ve ever dropped a ring, toy, or some other foreign object in a drain, you’re probably glad to have that trap there. It prevents small blockages from becoming major ones. This is also why when a sink is backed up, it is easy to access the trap and check for blockages.

Before it became U-shaped (or P-shaped as many refer to them), the trap was S-shaped. Its design allows water to pass through, while retaining a seal against the rise of foul odors, but when a drain is not used for some time, the water in the trap can dry out. If you have foul odors rising through your drains, something might be wrong with your sink trap or the water has dried out. If you have a bathroom sink in a part of the house that is not used frequently, we recommend running the water every month to ensure there is always water in the trap to prevent gasses from entering your home.

If you have a blocked pipe or a leaking sink trap, contact our plumbing team today. One of our expert plumbers can perform drain cleaning, plumbing maintenance, and plumbing repair. For additional information on plumbing services, call our team at 844-216-9300 and speak with a technician today.

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