How to Retrofit an Old Metal Drain Pipe to a New P-Trap
- 1). Turn the hot and cold water stop valves completely clockwise, shutting off any water to the fixture while you work.
- 2). Pull the wall plate from against the wall, if necessary, and slide it down the drain pipe a little, so that you have access to the nut underneath it. A wall plate would cover the end of the drain pipe, where it meets the waste pipe that protrudes out the wall.
- 3). Grip the nut on the end of the horizontal metal drainpipe, using a pipe wrench, and twist the nut counter-clockwise to loosen it. This section of pipe is also called the trap arm. Slide the nut down the pipe a little, so that you can remove the pipe from the metal waste pipe.
- 4). Place a bucket underneath the old p-trap to catch any water and debris stuck in it.
- 5). Loosen the slip nut on the end of the p-trap that connects to the horizontal pipe, using a pipe wrench. Do not totally unscrew the nut.
- 6). Unscrew the slip nut that connects the other end of the p-trap to the vertical drain tailpiece, using the pipe wrench. Remove the p-trap, dumping the water out of it and into the bucket.
- 7). Unscrew and remove the pivot nut and withdraw the pivot rod from the drain tailpiece, if the sink has a pop-up stopper assembly.
- 8). Twist the nut at the top of the drain tailpiece counter-clockwise, using the pipe wrench. Remove the tailpiece, along with the nut and washer underneath it.
- 9). Position a washer on the top end of a new PVC tailpiece, and slide the tailpiece up onto the bottom of the drain body. Position it so that the hole in the tailpiece, for the pivot rod to go through, faces the rear.
- 10
Tighten the tailpiece's mounting nut by hand. Insert the pivot rod into the tailpiece, through the stopper bottom, and tighten the pivot nut. - 11
Slide the end of the trap arm into the metal waste pipe that protrudes from the wall, and hand tighten the PVC slip nut. - 12
Hold the j-bend, which is the curved portion of the p-trap, in position underneath the drain tailpiece, to see if it reaches from both the tailpiece to the vertical trap arm. - 13
Attach a PVC trap arm extender to the trap arm, using a washer and slip nut, if more pipe is needed for the j-bend to reach from the drainpipe to the tailpiece. Hand tighten the slip nut. - 14
Place a washer and slip nut on each end of the new j-bend, and connect one end of it to the end of the extender. Hand tighten the slip nut. - 15
Slide the top of the j-bend over the bottom of the drain tailpiece. Tighten the slip nut by hand. - 16
Twist the hot and cold water stop valves counter-clockwise, to turn on the water. Run water down the drain, and look at all the pipe connections to locate any leaks. Turn off the running water, wipe the pipe joint connection dry with a rag and tighten the slip nut further with a pair of slip-joint pliers. Run more water down the drain to make sure all the nuts securely seal out leaks.
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