Can I Have a Garbage Disposal With a Septic Tank?

If you are coming from a more urban environment, where your pipes lead to a sewer system instead of a septic tank, you may think of a garbage disposal as a convenient appliance. You may think using one is a minor imposition on the system or no imposition at all. Or you may just not have thought about it at all.

But you need to understand that septic systems work differently from city sewer systems. Living with a septic system is a bit like moving to a foreign country. It’s a whole new culture, so to speak.

A septic system needs to be handled differently from a sewer system in terms of what you put into it and how you interact with it. Those differences in handling occur primarily in the form of modifying your day-to-day behavior at home.

You mostly won’t be interacting directly with the septic system. In fact, you want to interact with it directly as little as possible.

Instead, you will be interacting indirectly with it. But you need to understand that when you interact directly with household items like the toilet or disposal, you are interacting indirectly with the septic system.

You need to think about how you are impacting that system. ‘Out of sight, out of mind’ is a dangerous position in this case. It can lead to serious problems.

Convenience Costs

Let’s say you are peeling potatoes and historically you would have put those peels down the disposal. Now you are in a home with a septic system and wondering what to do.

Maybe you feel it’s a small thing and your other options are less convenient in the here and now. It seems like more hassle to put them in the trash can or start a composting heap.

Think again. That short term convenient answer can have substantial costs in terms of time, money and hassle.

Putting large quantities of food down the disposal when you have a septic tank can lead to increased clogs, the need to pump the tank more frequently and the risk that the tank will need to be dug up. If you think starting a composting pile is too much hassle, do you really want to spend additional time, money and energy scheduling septic tank maintenance and waiting around for a plumber? Can you even afford to take that many days off from work?

Why It Matters

Septic tanks are designed to handle human waste, not kitchen waste. Feces and urine are already broken down to some degree. Food waste from the kitchen is not.

Septic systems are already typically in a delicate state of health that is easily upset. There are lots of harsh chemicals you shouldn’t be putting down your sink or toilet because they can kill the microbes in the system that are breaking down wastes. Adding “foreign” matter that the system wasn’t designed to handle just makes this problem worse.

When you put food waste into the system, especially in large quantities, it changes the chemical and microbial environment. This actively interferes with the system’s ability to do its job.

Microbes are essential to the process of breaking down waste. Disrupting the microbial system causes the system to stop working.

Food wastes also tend to cause clogs in the system. This is especially true for some foods, such as fats and grease and foods that expand in water, such as rice and noodles.

Best Practices

In order to understand how to deal with a disposal when you have a septic system, you should understand how the system works generally. It will be easier to understand what you should and shouldn’t do if you have some larger context.

Let’s go over a little of that now, along with talking about some general best practices. Seeing what you shouldn’t do generally may help you better understand the restrictions on disposal use.

A septic system involves a holding tank and a leach field. No, it is not intended to be a permanent, maintenance-free solution. Although you need to be mindful of the chemical and microbial balance, it doesn’t simply break everything down completely where you can forget the tank even exists.

It needs to be inspected annually and pumped out about every three to five years. The more use of your system, the more your tank needs to be pumped out.

So as your family grows or if you start throwing more parties or otherwise having more people in the house, this will put a higher load on the system. If you misuse your system, this will also cause problems.

There are actually lots of videos on the topic of how a septic tank works. Here’s a nice illustrated video to get you started:

There are different kinds of designs. You should know which one you have and how it works. Here is a good overview of single compartment, double compartment and pump systems from the King County, Washington government.

Don’t put anything down the toilet other than toilet paper and bodily wastes. Do not flush household cleaners, diapers, tampons, condoms, cigarette butts, unwanted medication, oil or grease or any number of other things that people commonly put down toilets.

Be water wise. Running too much water through the system is a common cause of or factor in septic tank failure.

Be mindful of not negatively impacting the tank physically. This includes both landscaping choices and lifestyle choices.

You don’t want to use plants with deep roots that can invade the tank. You don’t want to park a car above the tank. It will impact the soil and can potentially break pipes.

Dos and Don’ts For Your Disposal

The gold standard rule of thumb is simply don’t use a disposal at all with a septic system. However, that may not be the most realistic expectation.

Maybe you moved into a house that already has a garbage disposal and a septic system. Maybe you have some reason why you feel you need to add one.

So let’s go over some other dos and don’ts. Hopefully, that will minimize problems if you do have a disposal in the house and a septic system out back.

• Do start a compost heap if you don’t like putting food waste into the trash. It can be a constructive and fun activity and doesn’t have to be particularly inconvenient.
• Don’t use small bones or the like as a means to sharpen the blades. Some articles recommend this method, but it is not a great idea to do this with a septic system as it just adds food waste to the system.
• Do sharpen the disposal blades periodically using a little ice and cold water. Ice melts and turn into water and won’t disrupt the chemical or microbial balance of the system.
• Don’t overload the disposal with too much ice when you do this! Ice is surprisingly hard. You can mess up the disposal. Don’t be fooled by the fact that it melts into water. It’s not water at this moment.
• Don’t overload the disposal generally by putting too many solids through it at one time. It can damage the blades and can cause clogging.
• Don’t ever put very tough fibers through the disposal, such as corn husks and onion skins. It’s hard on the disposal. It can damage it. Such things also tend to cause clogs. Stuff like this belongs in a trash can or compost heap, not your pipes.
• Do educate yourself about how the septic system works so you understand how and why your habits need to change. The information in this article is not comprehensive. This should not be the last thing you read on the topic if you expect to live with a septic system for the foreseeable future.
• Do commit to taking some time to develop different habits so you aren’t mindlessly mistreating your septic system. New habits take time and effort to develop. On the upside, once you have established new habits, good habits can be as hard to break as bad ones. This can make life easier for everyone.
• Do schedule additional appointments with a professional to have the tank pumped more frequently if you are using a disposal at all. You typically need to pump them out every three to five years and inspect them annually.
• Don’t put large quantities of food waste down the disposal. This is in addition to the rule about don’t overload your disposal. This is about what the septic tank system can handle. It can’t handle large quantities of food waste.
• Don’t listen to the messages from the disposal company saying it’s fine to use a disposal with a septic system. They are just trying to sell you something. They aren’t looking out for your best interests.
• Don’t put other trash down the disposal, such as paper, metal, glass or plastic. Yes, people have actually done this. Some folks have no clue how things work and find out the hard way.
• Do use it to break up food waste from the dishwasher. Some people find that the disposal gets filled with food waste from the dishwasher. Running the disposal about once a week can help clear this out and help your system work better.
• Don’t use harsh chemicals to clean the disposal. They will end up in the septic tank and can upset the chemical and microbial balance.
• Do use non-toxic cleaners to keep the disposal from smelling. If it smells, it’s probably germy. This is not good for your health.
• Do try ice first to clean the blades. See if that kills the smell before trying other non-toxic options. Remember that if it kills germs, it can still disrupt the balance of the septic tank system.

So, should I Use a Garbage Disposal with a Septic System?

If you have bought a house with a septic system and it doesn’t already have a disposal, don’t add one. It’s much easier to find other solutions if turning on the disposal is simply not an option.

In fact, if you have bought a house with a septic system and it has a disposal, you should consider having it removed. If you do so, get it removed by a professional plumber who can replace it with the appropriate pipes.

Yes, that’s counter-intuitive for most people. People typically don’t like giving things up. But it can’t be more expense or hassle than having your septic system pumped more frequently or having your septic system fail.

If you are renting a home and can’t remove the garbage disposal, then use it minimally. Generally speaking, the less you use it, the better.

If you are on good terms with your landlord, you might ask if they would remove the disposal.

Humans are creatures of habit and will tend to do what they have always done. It can be hard to get them to change their habits. Renters are notoriously bad about not knowing how to take proper care of the property. Some folks simply don’t care.

The bottom line is that garbage disposals and septic systems simply don’t play well together. It makes more sense to simply not pair them up in the same home, even if that means removing the existing garbage disposal, though it works just fine.