How do I identify the main drain when installing kitchen sink drain plumbing?

What You'll Need
•    Drain pipes with trap assembly •    Adjustable wrench•    Medium pipe wrench•    Bucket•    Teflon plumber's tape•    Towel•    Channel lock pliers

Old drains and traps and crack and leak, but you can upgrade the plumbing connected to kitchen sink drain with modern materials. Replacing the kitchen sink plumbing is a lot easier than you may think and generally doesn't take more than an hour.

Step 1- Shut off the Water

First, turn off the water supply going to the kitchen sink; to do this, simply rotate the valve handles that are near the bottom of the sink cabinet. They should be directly below the water lines that lead to the hot and cold water faucets.

TIP:Doityourself’s plumbing consultant Mark Vander Sande suggests, “The handles may not turn easily. Try a pair of pliers to turn them off, but do not force them. If they won’t turn, you may have to replace the valve. The packing nut may leak when you turn this valve off or back on again. It’s the large nut just past the handle. Simply tighten it a little bit and it will stop leaking. Don’t force it. You will break the valve off the pipe and have a flood.”

Step 2- Disconnect the Drain

To disconnect the drain from the sink, loosen the nut at the bottom of the sink drain with a large pair of channel locks, they’re easier to use than a pipe wrench. Slowly unscrew the entire pipe assembly from the area where it enters the main drain. This should be located somewhere near the center of the back cabinet floor. You should have your bucket ready to place under the drain assembly to catch the water that will fall from the trap. Be careful, this water will probably be very dirty.

Step 3 – Tape the Threaded Fittings

Using your Teflon plumber’s tape, wrap the threaded end of the trap and drain fittings with a piece of Teflon tape approximately 6 inches long.

TIP:Mark wants you to know, “It is very important to wrap the Teflon tape in the direction the nut will go on--right to left. If not, when the nut is installed it will simply remove the tape.”

Step 4- Connect the Drain

Attach the bottom part of the drain assembly onto the main drain, located at the rear floor or wall of the cabinet. Do not tighten it yet. Then, adjust the height of the drain assembly to where each side meets the appropriate hole on the bottom of the sink.

Step 5 - Secure the Drain

Using the pipe channel lock pliers, screw one side of the drain pipe assembly onto the bottom of the sink drain and tighten until it is snug and secure. Make sure not tighten the nuts too much or they will leak. Then, fasten the bottom drain assembly where it connects to the main drain. Again, do not tighten too much.

Step 6 - Turn the Water on

Rotate the shutoff valves to allow water to come back into the pipes. Open the faucets and check the entire drain, drain assembly and both water lines for leaks. If there are drips or leaks, tighten the connection slowly until the dripping or leaking stops.

Mark Vander Sande, professional plumber, contributed to this article.