01 of 06
There aren't many reasons for changing out the drain pipes under a kitchen sink, but one of the most common is during a kitchen renovation when the sink is being replaced. The steps for installing the sink drain will depend on how different the new sink is from the old one, as well as what other components are being installed. In older homes, the new sink may not be a different depth than the old one, so some alteration of the drain pipes may be necessary.
Tools and Materials You Will Need
- Kitchen drain trap kit
- Plumber's putty
- Channel-type pliers
Here are the steps for installing a sink drain from start to finish:Continue to 2 of 6 below.
02 of 06
Check the Drain Height
Deep sinks are very handy and stylish, but they take up more room underneath and may require that you lower the drain height to make them fit. Before you buy a kitchen sink, it is a good idea to check the height of the trap arm on the old sink, from the floor or base of the cabinet. Measure up to the center of the trap arm. If the height is more than 16", you may have a difficult time getting the necessary grade (slope) for the trap arm on the new sink, particularly if a garbage disposal is also being installed. Knowing the height of the existing drain ahead of time will help ensure that you are prepared and have enough time to lower the drain during the installation.Continue to 3 of 6 below.
03 of 06
Lower the Drain if Necessary
If you find that the existing drain is not low enough to accommodate the depth of the new sink, it may be necessary to open the wall and lower the position of the sanitary tee in the wall. This can be a somewhat complicated job that requires cutting away the back of the cabinet and the wall surface, so it may be a job for a professional plumber unless you are quite confident of your skills.
In our photo demonstration, the sanitary tee has been lowered. You may not have this situation in your own installation.
The general height to aim for is somewhere between 12" and 13" from the floor or base of the cabinet. This height will allow plenty of room for deep sinks and a large garbage disposer. Keep in mind that the drain height needs to leave enough room to remove the trap and clean it out if necessary in the future.
If you have lowered the drain tee, it is a good idea to wait to glue or tighten the fittings. Leaving them loose will allow movement and adjustments as you install the other parts of the sink drain.
The next steps will continue after you have installed the new sink.Continue to 4 of 6 below.
04 of 06
Install The Disposal and Strainer
Before installing any drain pipes, it is necessary to install the garbage disposal and basket strainer. Install the garbage disposal onto the desired side of the sink first, since this takes up the most space. On the other side of the sink (for two basin sinks) install a basket strainer.
This is also a good time to install any other under-sink components such as a water filter or a hot water dispenser.Continue to 5 of 6 below.
05 of 06
Connect the Continuous Waste Pipe
The continuous waste pipe is the piece that connects the two sides of the sink drain, and it should be installed next. Hold the continuous waste pipe up to the two drain ends and take a measurement for cutting the flanged tailpiece. If you have a garbage disposal, this measurement will between the sink strainer and the drain outlet on the disposal; if you have no disposal, just measure between the centers of the two drain openings. Do not overestimate the length, because the fittings need to be tight; you can always cut again if you cut them long the first time. Assemble the pieces in this order:
Continue to 6 of 6 below.
- Install the vertical flanged tailpiece onto the sink strainer first. Secure it with a slip nut slipped over the tailpiece and threaded onto the bottom of the sink strainer
- Slide the end of the continuous waste pipe into the side outlet on the drain tee fitting, then slide the assembly onto the sink tailpiece and garbage disposal drain pipe.
- Adjust the pieces as necessary, making sure the continuous waste has a slight downward pitch toward the tee fitting.
- Secure the slip nuts with channel-type pliers. These do not need to be over-tight; the plastic threads can be damaged if you use too much force.
06 of 06
Connect the Trap
The drain trap consists of a U-shaped piece and a J-shaped arm piece. The U-shaped piece will fit onto the bottom of the vertical tailpiece, while the arm is the piece that fits into the sanitary tee fitting at the wall.
- Assemble the trap and arm together loosely with the slip nut.
- Slide the trap up into the tee fitting on the sink drain, while sliding the arm of the trap into the sanitary tee fitting at the wall.
- Adjust as needed to create the most direct path from sink to wall tee. Make sure trap arm has a slight downward angle toward the wall tee. Note: Take care to face the trap the correct way. It may be tempting to turn it the wrong way in order to fit it into a small space, but it doesn’t work properly this way and has a tendency to leak.
- Tighten the slip nuts with channel-type pliers. Again, don't overtighten.
- If you have installed a new drain tee in the wall, now is the time to make sure all those joints are secure and permanent.
- Run water to check for leaks. Tighten up anything that leaks, and then fill up the sink and give it a good volume test. Do this for both sides of the sink to be sure everything is working properly.