The U-bend pipe under your kitchen sink helps transfer waste water to your home's sewer line and contains water in its neck that keeps sewer odours from escaping into your home. The pipe, also known as a trap, contains two nuts securing the pipe in place and is removable for cleaning and removing any debris. Like other plumbing repairs, gather all of the tools you need for removing the U-bend pipe before starting the repair process.
Place a large, old towel under the U-bend pipe you want to remove, then sit a bucket directly underneath the pipe. The bucket will catch any water present in the pipe and the towel will keep the area under your sink dry.
Use a plumber's wrench to remove the top nuts holding the pipe in place --- one on the upper portion of the U-bend leading to the top of the sink and one leading to the portion of pipe leading away from the sink. Turn the wrench counterclockwise to free the nuts then use your hand to loosen the nuts. Wear work gloves to get a good grip on the wrench and nuts.
Dump any water present in the U-bend pipe into the bucket. Place a piece of flexible wire or stiff brush into the pipe and pull it in and out to clean the inside of the U-bend pipe.
Flush the pipe with water from a water hose. You will see soap scum, grey matter and other debris exiting from the pipe --- this is normal debris present in the pipe.
Dry the U-bend pipe with a clean shop towel or rag. Reinstall the pipe under your sink carefully then turn the nuts clockwise with your hand to secure the pipe in place. Tighten the nuts gently with the plumber's wrench, but don't over tighten.
Turn on your kitchen sink's faucet to check for leaks and to fill the U-bend's neck with water for odour control. If the U-bend pipe is leaking around the nuts, tighten the nuts with the plumber's wrench.
Cut a strip of waterproof plumber's tape and wrap it around each of the pipe's nuts to seal the edges of the pipe.
Clean your U-bend pipe yearly to keep debris from building up inside of the pipe. You can also clean your kitchen sink's U-bend pipe using a liquid commercial drain cleaner, but the chemical may or may not flush out all of the debris present in the pipe.