What happens in the sewer if you pour fat down the drain?
You wash dishes and fat goes down the drain. So what?
People like to do things the easy way. If we can pour something down the drain or flush it down the toilet, it just goes away. Or so we think.
But that bacon grease, chicken fat, even vegetable oil causes big problems. Any fat down the drain can clog the pipes in your house.
Unless it causes the toilet to back up or you have to call a plumber, it may seem like just a nuisance. The worst problems happen when it gets into the sewer.
The water treatment industry refers to fats, oils, and grease collectively as FOG. FOG causes some 47% of sewer overflows—as many as 36,000 every year in the US.
When sewers overflow, raw sewage backs up into houses and streets. It can flow into rivers, where it becomes a problem for the water treatment plant to provide clean drinking water.
Streets flooded with sewage cause traffic backups.
The municipal government must use your tax money to clean up the mess. If a sewer backs up on private property, the property owner must pay to clean it up. If you own your home, that’s you, whether you poured the fat down the drain or someone else.
A little chemistry lesson about fat in sewers
Sewer pipe clogged with grease
Fat doesn’t dissolve in water. When you flush it down a drain or toilet, it finds other fat and clumps together.
It also adheres to the inside of your sewage pipes. Sooner or later, your pipes will back up.
Some people pour fat down the drain and then flush it with very hot water. That will indeed take it past your sewer connection.
Eventually the water cools, the grease hardens.
Now it’s solid grease again. It clumps together with the FOG all the other neighbors and townspeople have contributed. And clogs the sewer pipes.
Not only that, the fat combines with calcium found in sewer water to make something chemically related to soap. It hangs down from the top of sewer pipes like a stalactite. You wouldn’t want to wash anything with it. Just think of a bar of soap that gets bigger and bigger.
Sometimes these globs of fat become so big they’re called fatbergs.
A 40-meter long fatberg weighing 10 tons broke a sewer in Chelsea in London in 2015. Fixing it took two more than months, cost £400,000 and required replacing 39 meters of pipe, which was a meter in diameter.
London had to contend with at least two earlier and even bigger fatbergs. One found in Kingston in 2013 weighed 15 tons. One under Shepherds Bush Road, 80 meters long, in 2014 took crews four days to clear.
In London, the fatbergs are made worse because so many people there use wet wipes instead of toilet paper. But if fatbergs haven’t made headlines where you live, they have made headaches for your town’s wastewater treatment personnel.
The right way to dispose of waste fat
Even a little fat down the drain–from that bowl with lots of salad dressing to the fat people cut from their meat–contributes to the problem.
FOG belongs in the trash. If a fat will solidify, let it. You can put whatever it’s in in the refrigerator or freezer. Then it’s a simple matter to spoon it into a container (preferably not anything recyclable) and put it in the trash. Scrape plates into the garbage can using a rubber or silicon spatula.
Before washing a frying pan (or anything else with fat in it), pour the fat, oil, or grease into a container. Then wipe the pan with a paper towel before you wash it to absorb as much of the oil as possible.
Put the paper towel in the trash. Or, if you’re wiping up vegetable oil, you can add it to your compost pile. Just be sure not to add too much. It can form a hydrophobic barrier, meaning it will repel water and reduce its flow through your compost.
Don’t put a lot of liquid oil in the trash. It needs to go in a sealed can. Add some kind of absorbent material. Kitty litter or coffee grounds work. Or the paper towels you used to wipe the pan before washing it.
Some other environmental considerations
Many environmentally conscious people want to avoid paper towels. But when you stop to think about it, you don’t want to wipe up grease with a washable rag. That way you’ll only FOG up the sewer with fat down the drain from the washing machine instead of the kitchen sink.
Detergents dissolve fat enough to clean your dishes or laundry. Just not enough to keep it from congealing or clumping in the sewer.
Many fats are recyclable as biofuels. You can check to see if you live near a drop-off center that accepts used cooking fats.
Some jurisdictions require restaurants to install a grease trap to keep FOG out of the sewer. They usually have a grease barrel, anyway. You might find a restaurant willing to add your accumulation to theirs.
But whatever you do, don’t let any kind of fat, grease, or oil go down any drain.
Sources:
10-tonne fatberg removed from west London sewer / The Guardian. April 21, 2015
Cease the grease / Water And Treatment Education Roundtable
Fats, oils & grease: can the grease to protect your home, business and the environment / Arlington, Virginia Water & Utilities
Here’s the terrible thing that happens when you pour grease down the drain / Jennifer Welsh, Business Insider. August 29, 2014
How to properly dispose of grease and oil / Andy Orin, Life Hacker. May 2, 2014
Photo credits:
Greasy fat cooking Public domain from Max Pixel
Grease in sewer: Source unknown
In pioneer days people would combine their fats and wood ashes to make soap. As an incentive to get people to stop putting fats in the drain, a town could have an exchange. Drop off your solidified fats, we’ll give you free handmade soap.
There’s an interesting thought. In pioneer days, though, wood ash was the largest household waste by volume. Unless people have a wood fireplace, they don’t produce any wood ash at all. And remember, liquid fats in sewers are as bad as solid fats.
Hi dmguion. It’s true that most city people do not produce any wood ash. However, they might have scrap wood to donate rather than throw it out as they normally would. Pallets, old furniture, fallen trees could also be donated in exchange for a little free soap. Then you also need a wood stove on site to help process the wood. Even if the results aren’t perfect, you’ve still given someone an incentive not to put their fat down the drain. Hell I would be happy to save up fat in my fridge in exchange for free soap. And remember, soap also comes in liquid form for business’s to use in their bathroom. Win-win.
If you can get something started, let us all know! I’m certainly all in favor of using one problem to solve another problem and using waste materials as resources instead.