Can You Safely Use a Garbage Disposal With a Septic System?
Many people think that using a garbage disposal with a septic system will overload it and cause problems. But that’s not really true! You can safely use a garbage disposal with a septic tank if you follow two simple rules. First, make sure your septic tank is big enough to handle the extra waste. Second, only put food scraps or cooking grease down the drain — nothing else. Even though grease is often blamed for clogs, small amounts from cooking are usually fine for your system.
In short: Garbage disposals and septic tanks can work well together, as long as your tank is the right size and you’re careful about what goes down the drain.
Septic Tanks: What Are They and How Do They Work?
A septic tank is an underground system that holds wastewater from your home, including sewage. Its main job is to stop human waste from polluting nearby groundwater or surface water.
It usually has two parts: a primary chamber (where waste settles) and a secondary chamber (where air helps break things down).
When water and waste from your house flow into the tank, solids settle at the bottom and get broken down by natural bacteria. The leftover liquid, called effluent, flows out through a pipe and into a leach field or seepage bed. This process filters wastewater into the soil in a safe manner.
Thinking About Adding a Garbage Disposal?
If you’re planning to install a garbage disposal, you’ll need to make sure your septic tank is large enough to handle the extra waste. If it’s too small, it can cause clogs or backups in your plumbing system.
What If Your Septic Tank Is Too Small?
If your septic system isn’t big enough, you have a couple of options:
- You can add an extension chamber (also called an auxiliary or side-arm system), which typically costs around $4,000 to $5,000.
- Or, you can skip the garbage disposal altogether and compost your food scraps instead.
Further Reading: What Is a Septic Tank and How Does It Work? (Full Guide)
How a Garbage Disposal Can Impact Your Septic System
A garbage disposal grinds up food scraps into tiny pieces and washes them down the drain with water. These small bits then flow into your home’s septic system. Septic tanks break down waste with the help of bacteria. However, using a garbage disposal means a lot more food waste ends up in the tank, giving the bacteria extra work to do.
It’s not just about creating more scum on the surface — it also means more solids settle at the bottom of the tank, which take longer to decompose.
The upside is that since the food is finely ground, it usually breaks down faster and doesn’t overload the system — as long as your septic tank is big enough.
If your septic tank is too small, the bacteria may not have enough time to break down all the extra food before the tank fills up, which could lead to overflows or system problems. That’s why having the right-sized septic tank is very important if you plan to use a garbage disposal.
What Size Septic Tank Do You Need If You Have a Garbage Disposal?
There isn’t a special formula just for sizing a septic tank with a garbage disposal. A well-sized tank should already be able to handle the extra waste from the disposal.
Septic tank size is mainly based on how many people live in the house — or more specifically, the number of bedrooms.
For example, in a home with five bedrooms, a 1,500-gallon septic tank is usually more than enough.
When sizing a tank, experts consider:
- How much water the household uses daily.
- How long waste should stay in the tank (called “detention time” — usually about three days) so solids can settle at the bottom.
- How much sludge will build up over about three years.
Here’s a basic guide for septic tank sizes based on the number of bedrooms:
| Number of Bedrooms | Recommended Septic Tank Size |
|---|---|
| 2 Bedrooms | 750 gallons |
| 3 Bedrooms | 1000 gallons |
| 4 Bedrooms | 1250 gallons |
| 5 Bedrooms | 1500 gallons |
Further reading: How to Calculate the Right Septic Tank Size for Your Home
How to Prevent a Garbage Disposal From Overloading Your Septic Tank
1. Use Septic-Safe Additives
If you’re worried about your garbage disposal adding too much waste to your septic tank, using septic-safe additives can help. These additives boost the bacteria that break down food scraps, reducing the load on your system.
However, not all additives are safe. Always choose products that contain safe ingredients like nitrogen, potassium, and enzymes — and avoid harmful chemicals. Always check government or water company guidelines when picking an additive.
2. Check your garbage disposal before putting anything in it
Do not use bleach, lye, or phosphate-containing additives or cleaners on your septic system:
- Lye is highly corrosive and can damage your pipes.
- Bleach can kill the helpful bacteria your septic system needs to work properly.
- Phosphates can also harm bacteria and speed up corrosion of metal parts.
Instead, stick to safe biological additives like BioWonder or Septic Saver that support a healthy system.
3. Don’t Overuse the Garbage Disposal
Think of your garbage disposal as a helper — not a trash can. Try not to put every bit of food waste down the drain, especially after big meals or parties.
Overusing your garbage disposal can overload your septic tank and its pipes, leading to problems over time. By limiting how much waste you send down the drain, you’ll make your septic system last longer.
4. Avoid Dumping Large Amounts of Bleach or Harsh Chemicals
While small amounts of bleach in everyday cleaning water are usually fine, dumping a lot of bleach or harsh cleaners into your septic system can kill the good bacteria inside the tank.
Without enough bacteria, solids won’t break down properly, which can cause major issues. So, it’s important to use chemicals carefully and in small amounts.
Do You Need to Pump Your Septic Tank More Often If You Use a Garbage Disposal?
A lot of people think using a garbage disposal means you’ll have to pump your septic tank more often — but that’s not really true. Recent studies have shown that while garbage disposals do add more solids to the septic tank, the finely ground food particles break down easily. As a result, they don’t significantly affect how often you need to pump your tank.
Like I mentioned earlier, having the right-sized septic tank is very important if you want to use a garbage disposal.When more solid waste goes into the water, it takes longer for everything to settle and also leads to more sludge buildup at the bottom of the tank. If your septic tank is too small for the extra load, you might need to have it pumped out more often to keep it working properly.
Best Garbage Disposal For Septic Systems
As long as your septic system is properly sized, you can use any garbage disposal. The following are some of the best garbage disposals for septic tanks:
1. InSinkErator Evolution Septic Assist
InSinkErator’s Septic Assist garbage disposal is specifically designed for homes with septic systems. It comes with a small bottle of liquid enzymes that help support the good bacteria inside your septic tank.
2. Waste King L-3200
The Waste King L-3200 is a great budget-friendly alternative to the more expensive Septic Assist model. It has a powerful 3/4 horsepower motor that can easily grind up most food scraps, including tougher items like chicken bones and fruit pits.
Conclusion
Using a garbage disposal with a septic system isn’t as risky as many people think — as long as you take the right steps. By making sure your septic tank is properly sized, limiting what you put down the disposal, and using septic-safe practices like avoiding harsh chemicals and supporting bacterial health, you can enjoy the convenience of a garbage disposal without harming your septic system. Modern garbage disposals, especially ones like the InSinkErator Septic Assist or the Waste King L-3200, are designed to make this balance even easier.
At the end of the day, the key is moderation and maintenance. Treat your garbage disposal as a helper, not a trash can, and keep an eye on your septic tank’s needs. If you stick to these simple habits, you’ll be able to get the best of both worlds — easy kitchen cleanup without risking costly septic system problems.
