I regularly have heard/read the claim that flushing coffee grounds in the sink can 'clean pipes' and/or 'scrape dirt from the pipes' and so on. (Note this is almost the opposite of the claim this question) Is there any truth in this or is it just an urban myth? I would assume the latter but can't find any sources for this: I can certainly imagine coffee having some abrasive characteristics, but only when applied with pressure, which isn't exactly what happens in the drain pipes?


3 Answers 3


Quite the opposite, actually.

Avoid putting coffee grounds down the garbage disposal. They won't harm the garbage disposal and they'll actually help eliminate odors. However, they can accumulate in drains and pipes, causing clogs. Best to avoid.

Garbate Disposal Do's and Don'ts

Despite the old wives’ tale that coffee grounds down the sink each day is “good” for the plumbing, we at Atomic Plumbing are here to tell you the truth:

Nothing causes more blockages and clogged pipes than coffee grounds and grease.

Even if you don’t put them down the drain at the same time, they’ll meet up and form a sludgy impenetrable nightmare.

Atomic Plumbing & Drain Cleaning: Is it safe to dump coffee grounds down the sink?

Most household plumbing lines are small, and connect directly to pipes that are only slightly larger. FOG and foreign materials can easily block the sewage flow. A blocked sewer can be a worse problem than just inconvenient and unpleasant. A blocked sewer can cause and overflow that sends pollution to our bayous and Gavelston Bay.

Common enemies to our sewer system

... Coffee grounds and filters

City of Houston, Tx Public Works:Block Plumbing/Sewer Overflow

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    They are, supposedly, great for compost, so that's where all of my grounds go. Commented Mar 22, 2017 at 14:04
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    I am not sure if your sources can be considered reliable here. If coffe grounds actually would clean your pipes, I would still find it likely that a plumbing and drain cleaning company would advice against it, since they have no interest in you keeping your pipes clean yourself. Commented Mar 22, 2017 at 15:45
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    @Tor-EinarJarnbjo - You're not sure if people who professionally have to clean out clogged pipes are reliable for stating whether or not coffee grounds clog pipes? Really? You really think a company would risk their professional reputation by blatantly lying on a website, where their claims are visible to all and can be confirmed or refuted, and they could be sued in court for making false claims that led to major expenses for people who read the site? I find that to be a bit more specious than the sources cited. Commented Mar 22, 2017 at 16:14
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    @Tor-EinarJarnbjo - Look at the what's out there. All the professionals in the field are pretty unanimous in their statements. Are you claiming that ALL professionals in the plumbing field are crooks? I know what you meant, and it's a paranoid viewpoint. As I pointed out, self-defeating, given liability laws and their status as professionals. That's also why I posted the City of Houston's water utility site. What possible interest could they have in having the citizens completely screw up the water works? Commented Mar 22, 2017 at 18:23
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    Paranoid viewpoints and not believing whatever you find on the internet is the reason for this site. With your argumentation you could also prove the existence of God by linking to all the churches around the world. What possible interest could they have in having the citizens completely screw up their minds, if there is nothing to it? Commented Mar 23, 2017 at 9:49

This technique was mentioned in a WCBS-TV report in 2010.

Another great use for coffee grounds is as a drain cleaner. Mixed with hot water, coffee grounds can unclog a drain and help keep it smelling fresh. In the refrigerator it makes a great deodorizer because the grounds can absorb odors.

The article was passed around the web and eventually onto the lifestyle website Lifehacker. The Lifehacker article & comments expanded with a recommendation to use "very hot" water and that the primary benefit was as a de-oderizer.

The risk of clogging drains is overstated, but they should not be used in septic systems. According to disposal maker Insinkerator, coffee grounds don't cause issues with disposals or drains, but can cause problems on unclean plumbing Insinkerator Blog.

Coffee Grounds and Eggshells

There is often the question of using a disposal for eggshells and coffee grounds. In fact, neither of these materials is harmful to a disposal, and will pass through it without a problem. However, problems can arise with household plumbing – especially if it is older, or has not been cleared in some time.

Both coffee grounds and eggshells are sedimentary in nature, if too much is placed in at one time, or if the plumbing is restricted, it can create a clog or a ‘slow drain’ situation. Too help avoid any problems, feed these materials into the disposer gradually, and utilize a strong flow of cold water to help flush it through the pipes.

Several plumbing sites mention that coffee grounds are a form of sediment, & settle to the bottom of septic systems instead of breaking down TheToiletZone.

The EPA lists coffee grounds(along with all other food waste) as things not to put into a septic system How Healthy is Your Septic System

Don’t put food down your sink. Septic systems are not intended to dispose of food waste, coffee grounds, grease, or fat, and, in fact, they will harm the septic tank. Try using a compost pile for non-meat food waste; it will help you avoid paying for unnecessary septic system repairs!


No, it is advised that you DO NOT pour coffee grounds down the drain. According to this article on what not to put down the drain:

This needs to be avoided as there is almost nothing else that will cause your pipes to clog as much as coffee grounds will. When the grounds reach your pipes, they will form a thick sludge that is a plumbing nightmare.

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    Does this provide anything more than what was already said in the other answer?
    – JMac
    Commented Oct 10, 2017 at 19:10

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