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How to Unclog a Kitchen Sink

  • Transcript

    LESLIE: Well, clogged sinks are a part of life and in my house, it’s the kitchen sink that tends to clog the most often.

    TOM: And that’s not all that unusual. With all that food prep and scraps, even a sink with a disposer can get clogged. But if that happens to you, learning the right way to clear it will make the job go easier and prevent damage to the pipes and the plumbing equipment. Here to give us the proper steps to clear that clog is Richard Trethewey, the plumbing and heating contractor from TV’s This Old House.

    Welcome, Richard.

    RICHARD: Hi, guys.

    TOM: You’ve probably cleared more drains than you can possibly ever hope to count, too.

    RICHARD: Yeah, I’m always big right after Thanksgiving.

    TOM: Now, why would a kitchen sink, even one that’s equipped with a garbage disposer, still have a clogged-drain problem?

    RICHARD: Well, I mean the disposer is doing its job: it’s taking foodstuffs and grinding it up. And so, if it grinds it up well enough, it should go down the drain but it’s also a function of the condition of that drain pipe on the discharge side. We see kitchen sinks that have – the pipes have sagged and so it’s going to clog in that horizontal pipe that should be pitched.

    TOM: So part of the solution here is making sure that the plumbing drain system itself does not have any of the built-in obstructions that sometimes we see: the angular connections, for example.

    RICHARD: Yep. Underneath your kitchen sink, the type of drain pipes that are under there are usually called tubular. And they come together with a compression knot that you tighten up and there’s a gasket in there.

    But there’s all sorts of little baffles that are in the tees and they’re designed to keep the water from splashing up into the double sink. But that also becomes a choke point so oftentimes, it’s simplest to just take apart that stuff, clean it all out and then bring it back together again.

    TOM: OK.

    LESLIE: Is there a better material over the plastic fittings that are the tubular parts, that you should be using to sort of help things move more efficiently, like brass?

    RICHARD: It’s funny. As a licensed plumber, I’ve always used brass but – and more and more now as we do Ask This Old House, I’m finding that the plastic is easier to work with, it’s smooth on the inside, it lasts, it’s pretty inert. So, I’m being won over to the plastic world.

    TOM: Now, if you do have a clog in that drain system, is there – the first thing that most people do is reach for a plunger. Are there things like that that work or are you better off just going right under the sink and starting to take things apart where you can physically see what’s going on?

    RICHARD: Well, if you put a plunger on top of a kitchen sink that has a disposer, you run some risk of trying to drive that food through a very small aperture, which is that grinding wheel inside of a disposer. So, we’ve heard stories about people pushing so hard that the disposer just sort of explodes off the bottom of the sink.

    TOM: Wow.

    RICHARD: Most kitchen sinks have a trap that has a clean-out on it. And so the best way, really, in my opinion, is to get under there with a shallow pan, open up that little nut that’s on the trap – that’s a U-shaped fitting that’s under the sink. And that’s designed to trap sewer gases so they don’t come up and make a smell and that’s usually the place where it clogs and …

    LESLIE: Are we turning off the water before we tackle the …

    RICHARD: We don’t really have to as long as you don’t run the water.


    RICHARD: You know, this is on the drain line only.

    TOM: Now, what about drain cleaners? I cringe when I hear people talk about these but that’s usually a really bad way to clear a clog, isn’t it?

    RICHARD: Drain cleaners only seem to clear the hair off of the plumber’s hands. I’m no fan there, so I hope I don’t start a lobby against me. But nothing beats a mechanical cleaning of a drain pipe with a snake or some sort of mechanical device. So often, those drain cleaners go down there and they crystallize in there or they sit there and they become a place where you’re going to soften and eat up the pipes.

    You could use drain cleaners almost as a maintenance item to sort of keep organic stuff clear in the pipe but I would never do it in a standing clog that was – had a whole sink filled with water.

    TOM: Now, Richard, so many people are accustomed to just grabbing a plunger when a sink clogs. Is that still an effective thing to do?

    RICHARD: Yeah, it’s the first line of defense. Every house should have one. And that is used to try and drive and push pressure down to clear the stoppage. After that, the next thing you go for is a snake: a mechanical device that can drive a cable down through the drain pipe, down through that U-shaped pipe called the trap and mechanically clear that drain.

    TOM: Now, is your advice always then, whenever possible, to try to attack this clog right at its source? In other words, get under the cabinets and try to take things apart, identify the clog. If there’s any obstructions, put it back together that way?

    RICHARD: Yeah, most kitchen sinks, if you look there you can see that the tubular connections can come apart easily. There’s also generally a little clean-out plug at the bottom of that U-shaped bend called the trap. And then you can put a shallow pan under it, open it up and most of the foodstuffs can come out and then you can run a snake through it, either downstream or upstream.

    TOM: Good advice. Richard Trethewey, the plumbing and heating contractor from TV’s This Old House, thanks so much for stopping by The Money Pit.

    RICHARD: Great to be here.

    LESLIE: Alright. You can catch the current season of This Old House and Ask This Old House on PBS. For local listings and a step-by-step video on how you can unclog a drain and even others, visit ThisOldHouse.com.

    TOM: And This Old House and Ask This Old House are brought to you by GMC. GMC, we are professional grade.

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