People often wonder if they can flush unwanted food down the toilet. Sometimes parents discover that the toddler has flushed food he did not want to eat, and wonder if this will cause a sewage backup. Other people believe that food is biodegradable and therefore will break down in the sewage system.

You cannot flush food down the toilet. Doing so can clog your toilet before the food gets to the sewage system. If it makes it to the sewage main lines it will cause problems in the city’s wastewater treatment system. If you have a septic tank, flushing food can cause a complete system failure.

Sewage systems are designed to break down and process sewage and water. Any foreign matter, whether it is biodegradable or not, including “flushable” items, will cause a system to run sluggishly and may cause a system failure.

Read on to learn more about why you cannot and should not flush food down the toilet.

Flushing Waste Food Damages Your Home Sewer Pipes

It is important to know that most clogs will occur in your own pipes. When items such as food are flushed down the toilet, the first place they will likely get stuck is in the inverted U pipe inside the toilet. This inverted U keeps the smell from the sewer or septic tank from entering your house by creating a water plug in the pipe.

From there, the things you flush go into the main drain pipes which may involve a few elbows, tees, and other various bends. Every single bend and tee in the pipes is another chance for items to get stuck and build up a clog in your pipes. This clog usually builds up over time by one thing getting stuck and then beginning a dam in the pipe. By the time the sewage is overflowing into your home, you have quite a big clog in the line.

  • You will need to call a professional plumber to snake the pipes in your home to find the clog.
  • They may need to scope the line from the cleanout pipe to find where the clog is.
  • Clogs that can not be snaked will require that the pipe is unburied, cut out, replaced, and reburied.
  • Clogged sewage pipes can be incredibly expensive to repair and damage large areas of landscaping.

There is no good reason to flush food down your toilet. The damage it can cause can be catastrophic, especially if the pipes were already primed for a major clog.

Flushing Food Damages the City Sewer System

Most people do not give any thought to the city’s wastewater treatment facilities unless there is a major disaster that causes the system to malfunction and overflow. The fact is that the population of any given city can do a lot to make sure that their city’s wastewater treatment facilities do not have major obstructions that cause overflowing.

  • Residential flushing of fats is a major contributor to municipal sanitary sewer overflows.
  • When residents flush fats, oils, and grease down the toilet, it floats on the top of the water and hardens as it cools down.
  • Usually, this causes a clog in the residential pipes, but when it reaches the city’s main sewer lines it begins collecting on the tops of the pipes.
  • Over time this hardened grease, fats, and oil create a clog that builds on itself and acts as a glue for other items that should not be flushed until the sewer is fully blocked and overflows from the manhole covers.
  • Restaurants are required to have grease traps that guarantee that their grease waste will not end up in the city’s sewer pipes.
  • Residential homes do not have a grease trap requirement, so grease that is flushed down the toilet or rinsed down the drain will flow until it sticks onto a pipe somewhere and becomes a problem.

Once the waste reaches the city’s processing facility it is first screened for solid waste. Solid waste is garbage that has entered the sewage pipes. This can be diapers, wipes, food particles, or anything that was flushed down and is large enough to be collected in a screener. This waste is thrown away as garbage. Some cities have huge grinders that homogenize the garbage before the screening.

If you believe that you are keeping something out of the landfill by flushing it down the toilet, you are wrong. You are simply passing the problem down the line. The city residents pay for this screening, hauling to the landfill, and the screening system installation and upkeep through sewer fees.

Flushing Food Damages Residential Septic Systems

If you decide to flush anything besides human waste and water down your home septic system, you are guaranteed to create a problem in your own backyard. Residential septic owners must be extra diligent to avoid flushing or rinsing anything down the drain that does not belong.

Many homes with septic systems do not have food disposal systems in the kitchen sink. This is because even the ground-up food and coffee grounds do not decompose the same way that sewage waste does. Whole foods that are flushed down the toilet are even worse.

  • Foods add to the solid layer that is in the tank and increase the frequency of pumping needed to keep the tank operational.
  • Food upsets the bacterial balance in the tank. The bacteria that eat the solids and clean the water in the tank need extra oxygen to process the undigested food.
  • The extra oxygen is not available in the closed system, so the entire digestion and breakdown process slows down.
  • The water that is flowing from the tank through the distribution box and out to your leach lines is not as clean as it should be as it leaves the leach lines and enters the groundwater system.

There is even less room for error when it comes to a residential septic system versus a home sewer pipe system. Do not flush any non-waste items, including food, down your toilets when you have a septic system.

How the Septic System Works

The septic tank is a brilliant mini wastewater treatment plant. Most systems are very basic with the main tank, a distribution box, and a series of leach lines that slowly drain away effluent water.

Water and human waste are washed down the sink or flushed down the toilet, and go straight through the pipes into a septic tank located in the yard.

The contents of the septic tank are divided into three layers:

  • Scum on the top, which is things like soap solids, fats, and other things that can not be digested in the system.
  • The middle layer is a liquid that is being purified by bacterial digestion.
  • The bottom layer is the broken-down solids, also called sludge.

There are two baffles in the tank. The first baffle directs incoming sewage into the middle layer so that it can be digested by the bacteria in the tank. The second baffle keeps the scum layer in the septic tank and allows the liquid layer called effluent to drain into the distribution box.

The distribution box allows the cleaned effluent to enter the leach lines which slowly trickle it into the groundwater supply.

Why Food Breaks the Septic System

If the food waste that you flush or wash down the sink makes it to your septic tank, there are several ways that it causes damage.

  • Food waste such as fats, crushed eggshells, ground foods, and coffee grounds can clog the incoming baffle which will make sewage back up into your home.
  • Food waste becomes part of the sludge layer that requires professional pumping when it builds up. The more food waste you put into your septic tank, the more often it has to be pumped out.
  • Oils, fats, and grease will rise into the scum layer and build up in thickness. If this layer gets too thick it will either clog the second baffle causing overflow or worse, enter the distribution box.
  • If the scum layer gets too thick to be stopped by the second baffle and it enters the distribution box, then it will filter down your leach lines and clog them. This will require a complete leach system overhaul, and possibly a complete septic system overhaul.

In the worst-case scenario, your septic tank can back up into your yard. It will have to be dug up to be operated on. That will cost you thousands of dollars, tear up your yard, and fill the air with the smell of sewage.


There are no good reasons to flush any type of food down the toilet. If you have smelly foods to get rid of, you can put them in plastic bags and refrigerate or freeze them until garbage day then throw them out. Fill old plastic and glass containers with oil and drippings and put them in the garbage. Wipe out pans and pots with paper towels to remove the oil before rinsing them in the sink.

Flushing grease, oils, fats, food waste, and other non-flushables will cause big problems sooner or later either in the main city sewer system or in your own backyard septic system. Tens of thousands of sewer systems in the United States overflow every year because of homeowners who flush food and other foreign materials down the toilet.

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