3 Compartment Sink

How To Plumb A 3 Compartment Sink

Whether you’re talking about a house, a public space, or a restaurant, a 3 compartment sink is an important tool. The first compartment removes dirt through a scrubbing process, the second compartment allows you to rinse the dishes, and the third sanitizes them.

It’s great for people who prefer doing dishes by hand to using a dishwasher.

After the installation of the sink, you may want to plumb it. But plumbing a 3 compartment sink isn’t the same as plumbing a standard sink.

You’ll also need to take into account how the sink is set up and what style is being used.

Overall, though, the process is relatively straightforward.

What Tools and Supplies Will You Need To Plumb A 3 Compartment Sink?

plumbing sink
  • 2 inch drainpipe
  • Tools to remove and replace flooring
  • Plumbing kit for a 3 compartment sink
  • P-trap kit
  • Sandpaper
  • Wrench
  • Hacksaw

How Do You Plumb A 3-Compartment Sink?

The process can be broken down into six basic steps:

Step 1: Plan The Path For The Pipe

You need to plan what path your pipe is going to take. It’s important to plan ahead of time to make sure that you get the right sized piping and tools.

The better your understanding of the task ahead, the easier it will be to complete.

The first step in the preparation is to run a 2-inch drain pipe under your floor. It should connect your waste stack to the sink cabinet.

Don’t pull up the flooring and lay the pipe until you’re certain that you’ve taken the shortest path. Once the pipe is laid under the floor, it will need to extend up inside the cabinet to 5 inches below the sink itself.

Step 2: Separate All The Pieces

You should have a kit that contains all of the plumbing necessary for the sink. It includes your drain tailpiece, elbow, and center tee.

Unpack the pieces and separate them. It’s important to understand what each one does and where it goes.

The elbow piece is responsible for connecting the left and right sink bowls. You’ll also need to connect your drain tailpiece to the center drain.

Step 3: Mark The Cuts

Now that you have all the pieces separated, you can put in both the sink drain and the tailpiece. The tailpiece attaches to the drain.

At the bottom of the tailpiece, the P-trap assembly should be attached. Your PVC extension pipe should be connected to the P-trap’s end path.

This is all fairly similar to how you plumb a standard sink. You’ll move the P-trap and the extension around until you feel them touch the drain pipe.

This will tell you how much piping you need. Mark the length of pipe that’s necessary.

Then you can cut the drainpipe with your hacksaw. Any burrs should be removed using sandpaper.

Step 4: Cut Your PVC Pieces

Now that the drainpipe has been cut to the appropriate length, it’s time to cut the PVC pieces. Make sure that each piece of PVC piping is able to fit into the place that’s marked on the drainpipe.

You should look at the wall and determine where your drain is. Sometimes center-set drains don’t actually need any additional pieces to connect to the drain, because they will install in your P-trap kit without issue.

If your 3 compartment sink has an offset drain, the setup is just a little more complicated. You will need to connect the drain to the P-trap kit by using a flexible extension.

This extension helps move the water so it can drain outside your wall.

You need to have a flexible drainage system in this case, as you’ll need to curve the pieces to line up with the wall outlet. Center drains are much more straightforward because they tend to line up already.

Step 5: Install The Sanitary Tee and PVC P-Trap

You have the drainage system installed now. That process is relatively similar to that of a standard sink.

Now you’re going to install your PVC P-trap and your sanitary tee.

Place the tee with the sweep facing up and the outlet pointing at the P-trap. Your extension pipe and outlet should be the same size.

The kit will come with PVC cement, which you should use to attach your tee and your drainpipe. Then you can connect your tee and extension pipe so that water can drain from the sink.

There should be a tailpiece connected to your center-set drain. Install the P-trap kit to the bottom of the tailpiece.

Make sure it’s aligned to the wall.

If you find that you’re having trouble connecting your center drain to the P-trap, it’s also possible to use tailpiece extensions to connect the pieces together.

Step 6: Check For The Leaks

You’ve finished all the hard work of plumbing the drain. The next step is just to test the sink and make sure that all three compartments drain properly.

Look for any leaks below the sink or near the wall.

Make sure that all of the connections are tightened properly. If everything runs correctly, you’re good to go!

Does A 3-Compartment Sink Need A Floor Drain?

Whether you need a floor drain might depend on your circumstances. Different areas have different building codes and regulations.

There are also different installation and plumbing requirements for restaurants and other commercial spaces than for residential areas.

In many cases, the sink will be required to connect to the sewer by a floor drain. But you might also be able to use a wall drain.

It all depends on the type of sink and your local regulations, so you should make sure you’re familiar with these before you get started.


It’s a relatively simple process to plumb a sink with three compartments. You shouldn’t run into any issues with the installation.

That said, if you find that the process is beyond you, it’s always worthwhile to check with a plumber for their expertise.

The three compartments in the sink will save space and allow you to do more work in a compact area. If you’re in the restaurant business, these sinks also do a lot to help with dishwashing.