The one sink blockage you shouldn't deal with yourself according to plumbers

Kitchen sink blocked again? This is the most likely culprit, according to plumbers. And you should call in a pro to fix it...

Interior view of modern kitchen with worktop sink and shelf
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While most sinks get a little clogged and lazy every once in a while, if your kitchen sink is not draining and keeps giving you trouble, you'll need to find out what the issue is sooner rather than later. 

And while unclogging a sink is usually pretty straightforward, there is one instance where your best DIY plumbing skills just won't cut it. Professional plumbers name the number one culprit of a perpetually blocked sink and what it will take to unblock it.

Why is my kitchen sink always slow to drain?

One word: grease. Jake Romano, the manager of John The Plumber, goes as far as to say that 'when a kitchen sink is always blocking up, I'd be happy to bet money that you have quite a bit of grease and gunk in the drains.' 

Gene Fitzgerald, a certified plumber and Head of Content at Best Osmosis Systems, warns that 'unfortunately, even the best unclogging hacks hardly ever handle blockages caused by oil and fats.'

How can I get rid of fat deposits in my drain pipe?

You've probably guessed it: prevention is better than cure when it comes to most plumbing problems, and this one is no exception. Fitzgerald advises the common-sense approach: 'keeping your sink free from all kinds of oil is the best way forward. It's quite easy. Don't pour oils and fats into your sink drain if you want a clog-free sink.'

If you do have a situation where your sink is blocked because of grease buildup, it's time to call in a professional. Romano reassures homeowners that 'many plumbers and drain cleaning services offer Hydro Jetting. Hydro jets are powerful pressure washers with a long, flexible hose that can be pushed through your drain system. It's designed in such a way that it can move around bends in your pipes, and it can blast away years' worth of gunk in seconds.'

A closeup of kitchen sink and houseplants

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Unfortunately, 'if the grease is too thick or hard, you may be out of luck. Oftentimes, kitchen pipes need to be replaced due to the nature of grease clogs.' Only a certified plumber will be able to tell you whether your grease slogs are resolvable, so call one in anyway.

Why else would a kitchen sink not drain properly?

If you're certain that grease isn't causing the blockage, there are a few other things to consider. Romano says that 'if it's not a grease clog that's causing your issues, it could be incorrect slopes, pipe fittings, types of pipe, venting, or sewer issues. Sometimes, your best bet is to hire a professional with a drain camera that's designed for smaller pipes and have them inspect it.

'It's important to note that not all companies that offer drain inspection cameras are equipped with cameras that can navigate through 1 1/2 pipes. In fact, not many companies offer that camera - as they're easily damaged. So, I recommend asking the company first if they can inspect your system with the equipment they offer.'

Modern, bright kitchen with an enamel sink and sunflowers

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Finally, if you have a clogged garbage disposal, you may be putting veggie peels down it that are too large for it to handle. Loren Bottem, Pluming Field Manager with Genz-Ryan, explains that 'most disposals cannot cut up the peels into fine particles, so they get pushed down the drain hole. This is basically like shoving too much laundry into a laundry shoot.'

If this is your issue, the best solution is either to  'throw peels in the garbage/composting bin', 'or invest in a proper solid waste removal system (disposal) that can handle anything. For example, the InSinkErator XL1100 (can be bought at Walmart) can destroy nearly everything you put in its path! Many say it’s even better than a wood chipper.'

Anna is a professional writer with many years of experience. She has a passion for contemporary home decor and gardening. She covers a range of topics, from practical advice to interior and garden design.