Why Is My Kitchen Sink Clogged (5 Most Common Reasons!)?

Your kitchen sink takes more abuse than any other drain in your house. We tend to use our kitchen sink as a garbage can. Over time your kitchen sink can develop a clog, causing it to drain slowly or not at all.

This article discusses the five most common causes of a clogged kitchen sink.

5 Reasons Why You Have a Clogged Kitchen Sink

Kitchen sinks clog all the time. I mean, why wouldn’t they? We’re constantly putting things in the kitchen sink drain — whether purposefully or by accident — that shouldn’t go in them. But there are other reasons too. Let’s look at the top 5.

1. Corrosion

If you live in an older home with metal pipes, your pipes are definitely experiencing some corrosion. Corrosion does two things that increase your chances of a clogged kitchen sink.

  1. As pipes rust, they become rough inside, just like Velcro. Over time, waste sticks to the inside of your pipes, and then waste sticks to the other waste, and so on. It’s a vicious cycle!.
  2. Also, did you know that your pipes shrink in size? But it’s not how you’re probably picturing it. As pipes rust, the thickness of their walls increases. This is because rust is much less dense than cast iron.
The thicker a pipe’s walls get, the smaller (or narrower) the inside of it gets. This increases the likelihood of a clog.

2. Grease

Kitchen grease is the oily liquid that you find on your pots, pans, and baking trays after you cook meat. It is also created when you cook with butter and vegetable oils. When you wash dishes with grease on them, the grease solidifies inside your pipes. As the thickness of grease increases, so do the chances of a clogged kitchen sink.

clogged kitchen sink - grease buildup creates clog
Grease is usually a liquid when we are working (or cooking) with it. However, when it mixes with water and cools, it changes from an oily liquid to a hard gooey solid that sticks to the inside of your kitchen sink drain.

3. Foods That Expand

The longer you soak rice, pasta, beans, lentils, Brussel sprouts, or potatoes, the larger they become. Most of these foods are capable of expanding multiple times their original size.

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What we typically see is this: a homeowner will scrape off and wash a bunch of leftovers down the kitchen sink right before bed. By the next morning, the food will expand so much that the kitchen sink clogs completely.

clogged kitchen sink - foods that expand
Highly fibrous foods like rice or broccoli, or foods that expand in water like pasta, should never be placed down your drain. This is true even if you have a garbage disposal.

4. Heavy Objects

You should never wash heavy object down your sink. Common heavy objects include bones, eggshells, coffee grounds, and sand. These heavy objects in your kitchen drain mix with the grease inside your pipes and clump together. Because of the clumps’ weight, some of stick in the horizontal sections of your pipes.

clogged kitchen sink - egg shells in drain
Although hard to believe, the weight of certain objects — even eggshells — cause clogs in the horizontal sections of your pipe, which are only sloped at a quarter-inch per foot. A 48-foot long pipe will only drop 1 foot.

5. Hasn’t Been Used In a While

We see this one all the time: a homeowner leaves for vacation and when they get back, their kitchen sink has a clog.

Naturally, this is confusing for many people. How could it happen? Well, the answer is simple. Previously, the water was capable of passing through all of the sludge that had built up in your pipes. But after the pipes dry out from inactivity, the sludge, grease, and build-up become rock hard. This causes your kitchen sink to clog completely.

Final Thoughts

Hopefully, you now understand (and can prevent) the most common causes of a clogged kitchen sink. If you would like to learn more. And, along with the “Related Resources” below, here’s a bonus: To learn everything about garbage disposal.

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