How to Replace Drain Traps Using Slip Joint Extension

Written by dean roughton
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How to Replace Drain Traps Using Slip Joint Extension
A drain trap is the curved plastic fitting beneath the sink which holds water to prevent backflow of odorous gases. (modern sink image by nextrecord from Fotolia.com)

A drain trap is a two-piece plastic fitting that connects the sink drain tailpiece to the wall drain. Two kinds of traps are typically sold in the plumbing section of hardware stores, P-traps and S-traps. According to Wayne Roughton, a licensed plumbing contractor of nearly 30 years, "The National Plumbing Code says it is now illegal to use an S-trap unless replacing an existing S-trap." Therefore, be sure to use a P-trap unless you know for sure you are replacing an S-trap. A slip joint extension is used to extend the drain tailpiece to reach the drain trap.

Skill level:
Moderate

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Things you need

  • Replacement trap
  • Slip joint extension
  • Hacksaw
  • Pencil

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Instructions

  1. 1

    Remove the existing trap by loosening the slip nuts at the sink drain tailpiece and wall drain pipe. Trap slip nuts are designed to be hand tightened only, so you should not require a wrench. Note which piece is connected at the wall and which is connected at the sink, so you do not misplace the new trap pieces.

  2. 2

    Thread the two pieces of the new trap together, but do not tighten. You want to be able to swivel the pieces for the best alignment with the sink drain tailpiece and the wall drain.

  3. 3

    Attach the outlet part of the trap to the wall drain by first removing the washer from the outlet of the trap. The outlet will be the longer, straighter leg of the trap. Slide the slip nut onto the outlet followed by the washer; the washer will be pressed against the wall drain as you tighten the slip nut. Slide the outlet pipe into the wall drain two to three inches and connect by loosely threading the slip nut onto the wall drain.

  4. 4

    Swivel the curved part of the trap so it is directly under the sink drain tailpiece. If necessary, adjust the outlet part in or out of the wall drain to allow proper positioning. Tighten the slip nut at the wall drain once the trap is in position. Swivel the curved part of the trap away from the sink drain tailpiece to allow room to install the slip joint extension.

  5. 5

    Slide the slip nut of the slip joint extension onto the sink drain tailpiece followed by the washer. Slide the extension onto the tailpiece and tighten the slip nut enough to hold the extension in place. Do not completely tighten because you may need to remove the extension to be trimmed.

  6. 6

    Check the length of the slip joint extension by swivelling the curved part of the trap back around beside or under the extension. Loosen the slip joint nut at the drain tail piece and adjust the extension up or down as necessary. If there is enough room, insert the extension into the curved part of the trap. Tighten all slip joint nuts. If there is not enough room, mark the end of the slip joint extension where it would slide two to three inches into the curved part of the trap.

  7. 7

    Remove the slip joint extension and cut the extra length off using the hacksaw. Be sure to cut squarely and not at an angle, so that the pieces fit together properly.

  8. 8

    Reinstall the slip joint extension onto the drain tailpiece. Adjust it up or down as needed to fit into the curved part of the trap. Hand tighten all slip nuts.

  9. 9

    Check for leaks by stoppering and filling the sink. Then, release the water all at once and inspect the connections for drips.

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