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How To Replace a Sink Drain

One of the most common home repairs is replacing a worn and leaking sink drain, also called a p-trap. The p-shaped drain piping under the kitchen sink or bathroom lavatory is called a p-trap. This assembly is made up of two pieces. The wall bend is the piece of pipe that enters the wall at the back of the cabinet. The “J” bend is the next piece of pipe. It connects the wall bend with the tailpiece or drain extension, the pipe that extends from the bottom of the sink to the trap. P-traps are typically made of PVC plastic or chrome-plated brass tubing. They can also be ABS plastic pipe, which is common under sinks in mobile homes. Replacing a p-trap is not particularly difficult but there are a few “tricks of the trade” that will make your job easier.

Preparation

  1. Clean out the cabinet under the kitchen sink.
  2. Place a container under the p-trap to catch gray water that remains in the bottom of the p-trap.
  3. Gather some rags to clean up afterwards.
  4. Use rubber gloves to protect your hands and wear safety goggles in case any drain cleaner was poured into the drain.

Removing the old p-trap

  1. Use a pair of water pump pliers (also called “channellocks” in the plumbing trade) or a 14″ pipe wrench to loosen the slip nuts on both the wall bend and the J bend. Myths and old wives’ tales to the contrary, a monkey wrench or smooth-jawed Ford wrench won’t help you here. The proper tool will make all the difference between success and failure.
  2. Wiggle the p-trap to loosen the joints. Allow the water to drain into the container.
  3. Pull the p-trap J bend free and throw it away.
  4. Use a twisting motion and pull the wall bend out of the threaded wall connection.

Installing the new p-trap

  1. If you are installing a PVC p-trap, you will use plastic beveled cone gaskets. If the new p-trap is made of metal, you will be using square-cut slip joint gaskets. The two different types of gaskets are not interchangeable.
  2. Clean the threads of the wall connection.
  3. Inspect the vertical drain extension tubing that comes down from the bottom of the sink. Make sure it is clean, solid, and not corroded.
  4. Slide a slip nut and gasket, respectively, on the vertical drain extension pipe, also called a tailpiece.
  5. Place a slip nut over the wall bend so that it fits over the preformed seal on the p-trap end.
  6. Slide a second slip nut over the wall bend facing the wall connection followed by a gasket.
  7. Slip the wall bend inside the wall connection and start the slip nut loosely.
  8. Place the J bend over the vertical drain connection and align it with the preformed end of the wall bend.
  9. Start the remaining two slip nuts on that connect the vertical drain pipe to the J bend and the wall bend to the other end of the J bend.
  10. With one hand, hold the J bend in perfect alignment with the drain extension and tighten that slip nut hand tight.
  11. Follow the same procedure with the slip nut that connects the J bend to the wall bend.
  12. Using your pliers or wrench, give each slip nut an additional ¼ to ½ turn.
  13. Wipe down the drain piping.
  14. Turn on the water at the faucet and check your work for leaks.

Tips

If you are installing a metal p-trap, be sure you use brass friction rings between the slip nuts and the gaskets or the joints will leak.

When using pliers to install the new p-trap, be careful not to squeeze the pliers or you will distort the slip nuts and they will seem to have tightened up when, in fact, they are still loose and will leak. Let the pliers jaws do all the work of gripping and turning the slip nuts.

If your PVC p-trap leaks when you test it simply loosen the leaking slip nut slightly, realign that joint, and retighten the slip nut. If it still leaks, remove and replace the beveled gasket with a new one.

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