Re-plumbing a kitchen sink the right way:
It seems like every drainage I have ever seen for a double kitchen sink is exactly the same. The left sink gows down to a p-trap and the right sink has a garbage disposal that is plumbed above the one p-trap on the left. This is not a good way to plumb it at all! At the junction where the right drain meets the left, take a look at the tee connector used: it has a very restrictive deflector to make the water from the disposal go down only. Beginning with a 1.25" pipe, you actually only get half of this for each sink. I have had several situations that i have had to use drano and a plunger to unclog the sink and this is just unacceptable.
Each sink should have its own p-trap and avoid the restrictive deflector. I also like to use as much thick walled ASB pipe as possible. As the main drain line in the back of the cabinet, you simply install a wye connector. This does not have the restriction that the tee has at all and the more direct flow line is helpful too. The main drain is 1.5" ABS so why not make the entire line from there the same?
I began by removing all the drain lines except for the straight pipe coming down from the left sink. I went and bought (2) 1.5" ABS p-traps, a 2' piece of 1.5" ABS pipe, and two connectors from a glued fitting to a compression fitting. The compression part is for where the garbage disposal and left sink come from (the white pipe in the right picture). After some measureing and cutting, I assembled the new drain. All the abs is glued which is another upgrade from standard. No chance of leaks on a glue joint.
This was a quick 45 minute project that makes all the difference. For only about $15 I will never again have to plunge the sink. In addition, it drains faster which is always nice too.
This is by far the best way to plumb a kitchen sink! I advise you to take a look at your kitchen sink - I'm sure it is the standard plumbing used. Ever had a problem?