How to Extend a Sink Trap

Extending the sink trap is a project any homeowner can accomplish.

The project requires only a few tools and a basic understanding of plumbing. The purpose of the sink trap is to create a water barrier in the U-shaped pipe that will prevent sewer gas and noxious fumes from returning into the house. The pipe needs to be lower than the exit drain from the house, and this is accomplished by extending the drain and then extending the pipe that connects to the drain.

Examine the underside of the sink and see exactly where the drain from the sink stops. Measure the distance between the end of this pipe and the drain pipe. The drain is the pipe that exits the house.

Calculate the amount of pipe you will need. Simply add the distance of the space from the bottom of the sink drain to the top of the exit drain. Add three inches to this number. This will allow for the drain to be below the exit drain, which will allow for the water plug to form.

Cut the pipe to the length determined by your particular job. Attach the first piece of pipe to the sink drain using the pipe nut and the pipe wrench. Make sure that you coat the threads with pipe cement. Do the same for the exit section. This will attach to a 90 degree elbow that comes off of the exit drain per zoning laws.

Attach the U-joint pipe. This is a pipe shaped like a "U" that will form the water plug when the water pools inside of it. Place both nuts over the threads and tighten by hand, alternating turns. This will keep it level. Make sure that you have applied pipe cement to both ends of the U-joint.

Test the pipe for leaks by running water through it.

Things You Will Need

  • Two foot section of pipe (size depends on your drain)
  • Tape measure
  • Hacksaw
  • Pipe cement
  • Pipe nuts

Tip

  • Before starting any project that involves plumbing draining to the outside, check with your local zoning codes to assure that you are repairing to code and that the original job was done correctly.

About the Author

Philip Powe started writing in 1987 for St. Louis area newspapers. He has since written for "St. Clair County Historical Society Journal" and the "American Association of State and Local Historians Journal." Concentrations are in home and garden, philosophy and history. Powe holds a Master of Arts in intellectual history from Southern Illinois University.