We know all food is organic (made of carbon). So if we throw organic stuff down the drain, it should get decomposed by bacteria and shrink. So why should we be worried about blockages if all the food will get decomposed and the drain will open up? I understand oil and grease is bad because it deposits and narrows the lumen of the drains. Plastics, are non-biodegradable hence will not decompose and should not be put down the drain.

So isn't it okay to throw food down the drain, because it'll never cause a blockage?

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    This question appears to be off-topic because it is about a non-culinary issue, to wit sewer management. – SAJ14SAJ Mar 12 '14 at 14:20
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    Decomposition is not instant. If you add grease faster than it breaks down... – derobert Mar 12 '14 at 14:39
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    @SAJ14SAJ : I consider questions about proper disposing of waste to be on topic ... like the questions about fats down the drain. – Joe Mar 12 '14 at 14:53
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    I think it is in topic because it principles like "clean as you go" while cooking – Pranay Aryal Mar 12 '14 at 15:03
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    No one has mentioned septic systems. If you're on a septic system rather than a municipal sewer system, putting food down your drains is a very bad idea, particularly oil. A garbage disposal is an even worse idea because it creates particles small enough to make their way into the drainage field and clog it. The resulting repairs can cost 10s of thousands of dollars. – Carey Gregory Mar 13 '14 at 15:22

It's not safe to assume that food won't cause a blockage if there are other processes at work.

I've known multiple people who have had tree roots manage to break into their sewer pipes. (odds are, there was a leak of water, the roots went towards it, and then opened the pipe up further). If the drain is already restricted, larger particles can make the situation problematic.

In my case, when the state highway was installing sidewalks and curbs on my street, their contractors ended up crushing sewer lines along our side of the street. I know that at least four of us were affected, as we started having issues with blockages and basements getting flooded by sewage ... but it took a couple of weeks for other matter to start filling in the crevices until we reached a complete blockage.

Even in the case where you don't already have an obstruction in your pipes, garbage disposals are quite inefficient as a way of disposal; you're wasting clean water in the process, and you're putting extra work on the sewage treatment plants.

Sewage treatment plant are designed to handle a specific volume of water and waste, and in cases of periods above their capacity, they may have to divert untreated water and hope that dilution will be sufficient. This means increased nutrient loads in your waterways, which can cause algae blooms and kill fish populations. (although the unprocessed food isn't as bad as the other stuff that's typically in wastewater).

Most carbon digestion is an aerobic process, with the result of the breakdown of food in the wastewater using up the oxygen in the water. Discharging this low-ox water can also lead to deadzones.

You also have to look at what a treatment facilities does with their extracted solids. In some newer facilities, there is biogas extraction, and the decomposition of the materials is used to power the facility. (sometimes, with excess capacity sold off). In others, they have to truck it away ... sometimes it's spread on fields as ferilizer. Other times it goes through a 'de-watering' process ... either pumped to the bottom of a lagoon to digest or spread out into troughs to air-dry, then hauled to a landfill for disposal.

Garbage disposals are convenient, and they're useful for the occassional scraps ... but if you can, compost your food scraps. As for normal garbage vs. garbage disposal, there too many local factors -- if you're in a water restricted area that doesn't have a biogas system or sufficient capacity at the water treatment facility, normal trash is likely your best yet. If you're in an area with lots of water, sufficient treatment capactiy and a biogas system, garbage disposal may be better.

For more reading on some of the hidden costs of garbage disposals, see:


Quite simply: it's not going to decompose and unclog itself. Decomposition is a slow process. Maybe the clog will eventually decompose enough to wash through, but even if it "only" takes a few days, that's a few days you'll be spending with a sink that's at best useless and at worst stinking up your kitchen.

And it'll likely be a lot slower than that. And your pipes aren't good conditions. The bacteria doing the decomposing need oxygen, and since your sink is clogged, there'll probably be water on top of the clog, not air. Unlike a large natural body of water with plenty of circulation to keep the dissolved oxygen coming back in, the clog is in a narrow pipe with a very limited amount of oxygen. The decomposition won't be efficient - more like weeks or months.

So sure, you can certainly put tiny scraps down the sink - crumbs, or larger things that've been pulverized by your garbage disposal - but anything that might clog the sink, you should dispose of another way. The things that can clog your sink, besides obviously larger particles, are generally heavy things (they'll sink in water) like egg shells. For all this stuff, while it's best to compost anyway, even if all you have is trash, it's still better to have a bit more trash than to clog your sink all the time.

  • Really, anything put down the sink should also be pulverized to a fine slurry by your garbage disposal, or be a pure non-fat liquid (like flat soda or spoiled orange juice). You should never, never put chunky solids down the drain. – SAJ14SAJ Mar 12 '14 at 22:43
  • @SAJ14SAJ Clarified, definitely didn't mean to suggest putting a potato down there. – Cascabel Mar 12 '14 at 22:46
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    If it sinks in water, it's going to sink in your sewer line. Making a fine slurry will help, but some things, such as lime water (CaO/CaCO3) from nixtamalizing corn do NOT belong down the drain. You'd just as well pour sand down there. – Wayfaring Stranger Mar 13 '14 at 0:31
  • Depends on your plumbing system. Out our way pipes are big, and septic system are biodigestors so they cope with anything that fits down the sink filter, say 5 x 5 mm profile – TFD Mar 14 '14 at 10:33

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