Is a garbage disposal bad for a septic system?

Garbage disposal system installed under a kitchen sink in a residential property.

Rather than putting food scraps into the trash, many homeowners put them into a garbage disposal (also known as a garburator) mounted under their kitchen sink. This system grinds food into tiny pieces that are then washed down the drain.

The technology works well enough in communities with municipal sewer systems. But is it wise to install a garbage disposal if you own a home with a septic system? From our perspective, the simple answer is no.

We recommend that you avoid using a garbage disposal with a septic system for three reasons:

  1. It reduces the effectiveness of your septic system.
  2. It creates additional expenses.
  3. There are greener ways to dispose of food waste.

It reduces the effectiveness of your septic system

Wastewater solids that sink to the bottom of your septic tank are called sludge. In healthy tanks, bacteria have enough time to break down organic matter and keep sludge levels in check.

Simple two-dimensional diagram of sludge levels rising in a residential septic tank.

You overwhelm these bacteria if you continually put pieces of food down a garbage disposal. When this happens:

  • sludge levels rise
  • the capacity of your tank decreases
  • the ability of bacteria to treat wastewater diminishes

It creates additional expenses

If the bacteria in your septic tank do not have enough time to break down food particles, sludge levels are sure to rise. That means your tank will need to be pumped more frequently — up to twice as often according to some estimates.

The average price to pump a septic tank in Canada is about $300. For most homeowners, the advantages of garbage disposals seem small compared to the cost of additional pump-outs that could otherwise be avoided.

There are greener ways to dispose of food waste

Vegetables, fruits, and other food waste in a wooden compost bin located in a back yard with green grass.

Garbage disposals do not solve the problem of food waste — they merely deflect it.

Composting is a more environmentally responsible approach. It transforms organic waste into a sustainable and natural resource that adds nutrients to lawns, gardens, and flowerbeds.

This strategy is so simple that anyone can make it work. All you need is a compost bin or compost pile, a bit of know-how, and a place to spread the finished material.

The beauty of compost is that it has practical uses for gardeners and non-gardeners alike. With it, you can:

  • fertilize lawns and gardens
  • make potting soil for indoor plants
  • create moisture-holding mulch
  • help a neighbor who has a green thumb
  • support your local community garden

Tips for using a garbage disposal with a septic system

Vegetable peels and other food scraps being flushed down an Insinkerator Evolution garbage disposal system.

Not everyone will follow our advice about garbage disposals and septic tank systems. If you choose not to, here are a few tips to help you avoid problems.

What can you put in a garbage disposal? 

Garbage disposals are designed to dispose of soft foods and non-dairy liquids. The following items are safe:

  • fruit flesh
  • soft and non-fibrous vegetables
  • ice cubes
  • biodegradable dish soaps

What not to put in a garbage disposal with a septic tank

Garbage disposals are designed for easily biodegradable food scraps. They are not equipped to cope with:

  • fruit pits and peels
  • stringy or tough-skinned vegetables (especially celery, corn husks, and artichokes)
  • onion skins
  • eggshells
  • pasta, rice, and oats (they expand in water and can clog your pipes)
  • nuts
  • meat
  • bones
  • coffee grounds
  • potting soil
  • fats, oils, and greases (including dairy)
  • non-food items like plastic, paper towels, and twist ties

Even if these items pass through your garbage disposal, they will not decompose inside your septic tank. Instead, they will accumulate until a pumper removes them.

Hot or cold water down a garbage disposal?

Food waste is more likely to get stuck in your garbage disposal or septic pipes if it is warm. Avoid clogs by running a steady stream of cold water just before and while you grind food in your system.

Regular maintenance is critical

Take care of your garbage disposal by maintaining it according to the manufacturer’s instructions.

Preventive action is also the best strategy to keep your septic system running smoothly. Have a professional regularly inspect your installation and measure the sludge in your septic tank. If it is time for a pump-out, book your appointment as soon as possible to avoid system failures.

If disaster has already struck, we can help

Garbage disposals are not the only culprits when it comes to sewage backups and clogged drain fields. If you are experiencing any problems with your system, our septic service team is available to help around the clock.

Discover our septic services

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