THE KITCHEN GUIDE BOOK

Kitchen plumbing is not overly difficult if you have a little plumbing experience. always verse yourself with the local plumbing codes. Hire a professional if you are not comfortable with DIY.

Aside from the refrigerator water line, kitchen plumbing is all about the kitchen sink area. Rough Plumbing a kitchen sink starts with an accurate cabinet plan, (The Cabinet Design Layout Page). The exact location of the sink cabinet must be known to know where to locate the rough water supplies and the sink drain.

                                    Kitchen Drain Sink Area

At the kitchen sink the type of sink can affect the placement of the rough drain. Under mount sinks and deep sinks lower the drain lines and the disposal. The height of the drain line coming out of the wall should be 16" up off the sub floor to the center of the pipe, unlike the old rule of 18". If the sink is available you could hook up the drain assembly and get an exact measurement from the top of cabinet down to needed height of the drain outlet. Kitchen sink Information page.

Kitchen rough drain lines are usually 2" PVC or ABS pipe. Leave a compression fitting a few inches into the cabinet from a sanitary t. The sink vent goes from the top of the sanitary tee to out the roof. 

Inside the sink cabinet connect the disposal and sink drains to a trap and then to the rough drain at the compression fitting. The under the sink fittings and trap are usually 1-1/2" compression PVC for kitchen sink plumbing. See example below.
              
The dishwasher drain needs some sort of air gap to prevent reverse siphoning. Air gaps can be accomplished by a separate trap, an air gap fitting on top of the counter top, or just a high loop in the dishwasher drain hose attached to the inside of the cabinet and then to the disposal as in the picture above. Rely on the specific dishwasher installation instructions, and your local codes. 

                                 Water Lines at the kitchen Sink

Kitchen plumbing the rough water supplies for the faucet should come out on either side of the drain, and are usually 1/2" copper, PEX, or CPVC that are connected to a shut off under the cabinet. It is a good idea to have a T off of the hot water supply with a separate shutoff for the dishwasher because if the dishwasher brakes you will still have the sink working. The flexible type supply lines from the shut offs to the faucet are a little more expensive but are the best option. Some faucets come with their own supply lines attached. the shut offs should have the 3/8" fitting for the supply line side.

If your new kitchen has the plumbing in the same place then still a good idea to change all the old drain lines, shut offs and water supply lines so they last another 10 years till the next kitchen remodel?