How to Fix a Kitchen Sink Drain

Learn how to fix a kitchen sink drain from Master Plumber John Wood in this plumbing repair video from Howcast.

Okay, folks. So, today, I’m going to show you how to fix a kitchen sink drain. This is a very common repair, because they rot out quickly. The material that you most commonly see under a kitchen sink is this brass, here. This is 17-gauge brass, which is actually referring to the wall thickness of this pipe. This is called a tailpiece. In particular, this is a flanged tailpiece. You can see that flange.

Behind me is a sketch of a sink, all right. This item here is called a basket strainer. You’ve probably seen this in your own sink. This is the stopper that you use that catches all the food. And below that, is the part that’s permanently affixed to your sink; this is the basket strainer itself.

So, for our purposes today, I’ve illustrated the basket strainer here, okay? This is the basket strainer, this assembly right here. And this, right there, is the tailpiece. So, when you get a leak below your kitchen sink, when you have a leak, all of a sudden, you open the cabinets one day and there’s water below. Most likely, this, or some portion thereof, has rotted out, cracked, decayed; it’s time for it to go. So, you need a few tools to get this done, okay?

Once again, a Channellock. This time, we want them with the teeth. The reason I have two pair is so that in case I need to hold back, I can turn like so and gain torque that way. I’ll demonstrate that in a moment. The other is a 20-cutter. 20 is the number of the cutter, okay? This is a big cutter so that you can get around this pipe to cut it, all right? Most likely, this comes at a standard 12-inch. You’ll probably have to cut it to some length, depending on the height of your trap. The trap is that you shape the piece of pipe right there under every kitchen sink. And if it’s not under your sink, it should be under there because somebody did something wrong.

The purpose of the trap is to keep water in that U. To trap everything in the sewer, out in the sewer. Things like flies, bad smells and sewer gas, more dangerously. So, imagine the water level in the trap will be sitting right here. So, when water goes down from the sink, it goes out into the drain and out into the sewer. But that little U-shaped piece of pipe, the trap, keeps a little bit of water there to keep everything on this side of it, the street side we call it, out there.

Now, when removing a basket strainer from an existing sink, it can kind of get hairy. So, imagine this basket strainer living in there for 15, 20 years. So, we’ve got the nut that holds the assembly onto the sink, like so. With time, that nut can fuse on and it gets really difficult to remove. So, the only caveat there, you might have to hire a plumber, because we need to get in there with a saw and cut it out and it can be a nightmare. If it’s not and most of them aren’t, you can use this tool here. There’s no other purpose for this tool in the world other than that brass nut on the bottom of the basket strainer. It is designed solely for this brass nut.

It fits on like so. See the little nubs on that nut? It grabs perfectly and you can turn that nut like this, okay? This is essential. A lot of guys, a lot of plumbers or homeowners, you can get the job done with the Channellocks but what you have to do and it’s a pain, is grab those two nubs and then you get what I call the "knuckle buster." It slips, boom, and you smash your knuckles between the Channellocks. And then the next thing you do is throw them behind you. Probably hit your wife or husband or whoever’s behind you and we have a bad day. So, I have the right tools for the job.

Let’s say we’ve got the basket strainer out and now, we’re looking at a kitchen sink that’s just a steel sink and there’s a hole there. What you’re going to do is take this piece here, this collar, as we call it. Put a roll of putty around that collar and smush it down into the sink. That putty is going to kind of keep it there.

Okay, now, our head will be up here above the counter top. We’re going to go beneath. What you’re going to see are these threads here, okay? If I’m going to refer to my drawing, now we’ve got this collar stuck down into the sink. And we see these threads down here. Now, we can concentrate on putting the basket strainer assembly together.

So, from under the sink, again, we’re looking at these threads. Your drainage assembly will come with these two gaskets. One is a cardboard gasket. The other is a rubber gasket. The rubber gasket is what makes a watertight seal. The cardboard simply kind of holds it in place. So, you would, again, looking at these threads underneath, put these up, like so. Then you’re going to take your brass nut. This wide brass nut, this retaining nut. You thread the brass nut on. You can do this by hand for a while. And then, you’re going to get down to the business end of things and you’re going to start building up torque, okay? Start building up torque.

When you start building up torque and you can no longer turn it with your hand, you get on it with this strainer nut wrench. And with quick, jerky movements, I’m going to turn to the side, so you can see. This would be you looking underneath the sink, straight-up, okay? You kind of get on it, turn, turn, turn and it’s going to build up torque. And you’re going to be able to feel this whole assembly kind of snug down to the sink, okay? Again, with the sink being the steel of the sink being between these gaskets and this top chrome collar piece. Very simple. Very, very simple. You can save yourself a lot of money by doing this yourself.

So, now we’ve got our basket strainer assembly on the sink. It’s solid, it’s in place, okay? Now, this is all brand new; there’s nothing leaking. So, this is a common leak because there’s a rubber gasket here that wears out. Now, you will have taken this out because this is the most common culprit. It rots through and it’s very, very thin. And when it gets old, you can actually just kind of crush it like a soda can.

There are a couple of nuts that attach this to both the basket strainer and your trap. This is called a slip nut, a brass slip nut. You can see real cheap ones at the supply houses and stuff. But this is probably about $6, this nut. This heavy-duty brass one. It won’t dent and it will be there long after you and I are gone, most likely.

So, this nut here would go over that flanged tailpiece. Again, what stops this from sliding straight out is the flange. This is what’s going to attach underneath the sink to the threads remaining on that basket strainer. Your flange goes straight up and meets. As you can see, it’s the same size, okay? But, this is critical. You have to put this special little gasket in. Generally speaking, this gasket, called a top hat gasket because it looks like a top hat if you can see that, okay? Looks like a top hat that you’d wear.

This is designed to sit right in there. As you can see, it won’t fall out. And this is what makes the watertight seal. Because if you put metal to metal, it’s going to leak. There’s not enough of a seal. This, as it compresses, you can just kind of screw that on. And you can feel it. You can feel it snug down and it stops. You only really have to do this hand tight. But just for safety’s sake, I’ll give it another snug with the Channellocks and it’s down. But now, you’ve got a watertight seal here.

The last thing that you have to worry about is the nut going down to your trap. Now, generally speaking. So, again, we’ve got a fully-assembled sink now, okay? Generally speaking, we’ve got a trap; that U-shaped piece of pipe right here, okay? And the trap on the inlet of the trap, that’s what we call the inlet, where the water goes in. This being the outlet. On the inlet of that trap, there will be threads. And it’s exactly the same type of nut, just a different finish. Goes over.

And then, we use a slightly different gasket. This is called a beveled slip nut gasket, okay? It’s beveled as you can see it. You just hold that up. It bevels in, so it creates this kind of depression where once slipped over this tailpiece, this nut is going to compress that; you don’t see it. This nut is going to compress it down to the threads on the inlet of the trap and again, create a watertight seal. And that’s how you fix a kitchen sink drain.