Dual P-Trap

A second P-trap on a dual-basin sink can eliminate drainage problems.

Problem: Your dual-basin sink doesn't drain properly. When one side drains, the other side begins filling up.
 
Solution: It's easy to install a second P-trap to eliminate this problem.

Equipment list:
Adjustable pliers
Screwdriver
Saw for PVC pipe
Safety glasses and gloves
Hacksaw
Tape measure
PVC glue
PVC cleaner

Materials include:
2 traps
2 straight elbows
Some short straight pieces of PVC pipe
2 tailpiece adapters
Double-T connector
Extension piece with rubber coupling to connect to old system

1. Remove all the old PVC pipes except for the one leading to the wall or floor. Be sure to place a bucket underneath the drain before you remove any pieces. You may have to saw off the existing elbow to create a straight line into the main drainpipe.
2. While the main drain line is accessible, you can root it out with a plumber's hand snake to reduce the likelihood of future clogs.
3. Attach the rubber coupling to the main drainpipe and tighten the clamp. The coupling allows you to fit a larger pipe to a smaller one.
4. Place a trap adapter fitting on the strainer tailpiece.
5. Attach a 90-degree elbow to the P-trap.
6. Measure the distance between the trap adapter fitting and the location you expect the trap to be in after it is fitted to the drainpipe.
7. Cut a PVC extension pipe to that length using a PVC saw.
8. Weld the P-trap to the PVC extension with PVC glue.
   1. Open a window and put down a drop cloth. Be sure to wear your safety glasses and gloves.
   2. Prime the area to be glued. The primer has a purple dye that lets you know it is saturating the PVC material.
   3. Apply the glue by smearing it around the area to be connected.
   4. Press the fitting together, give it a half-turn and hold it for 25 to 30 seconds.
9. Attach the extension to the strainer tailpiece.
10. Hand-tighten the trap adapter compression nut.
11. Repeat the process for the second drain.
12. Install an end cleanout on the double-T fitting for easy cleaning access later.
13. Attach the 90-degree elbows to the P-traps and point them toward the double-T fitting; don't glue them yet.
14. Hold the double-T fitting in the location it will be in when it is linked up with the traps and drainpipe, and measure the gaps for three extension pieces. Cut the pieces and weld them to the double-T fitting.
    * Remember which piece goes where.
15. Fit the extension back into the drain coupling, but don't tighten it yet.
16. Add primer and glue to the trap elbows and make the final connections.
17. Tighten the adapter collars, clamp on the rubber coupling and tighten any other connections.