Aerobic vs. Anaerobic Septic Systems: Which One Works Best for Your Home?
You Have to Replace or Install a Septic System—Now What?
You didn’t wake up today excited about septic systems, but here you are. Maybe your old system is failing. Maybe you just bought property and need a new install. Either way, the last thing you want is to make the wrong choice and regret it years down the road.
If you’re like most homeowners near Olympia or Pierce County, you have concerns. You want a system that works, lasts, and doesn’t cause expensive headaches. You’ve heard about aerobic and anaerobic septic systems, but you’re not sure which one makes the most sense for your home.
We get it. At Southbay Septic & Excavation, we’ve worked with homeowners across Thurston, Pierce, Lewis, and Kitsap Counties, and we’ve seen what happens when people install the wrong system for their needs. So, let’s break it down in plain English—so you can make the best decision for your home and avoid costly mistakes.
What’s the Difference? Aerobic vs. Anaerobic Septic Systems Explained
The main difference between these two septic systems comes down to oxygen.
Aerobic systems use oxygen-loving bacteria to break down waste.
Anaerobic systems use bacteria that thrive without oxygen to do the same job.
Both systems process wastewater, but they do it in very different ways—and that impacts everything from maintenance to lifespan to cost.
Why Your Septic System Choice Matters in Pierce County
Before we dive into how each system works, let’s talk about why this decision matters—especially if you live near Olympia, Tacoma, or the surrounding areas.
Soil Conditions: If your property has poor soil drainage, you might need an aerobic system.
Size of Your Lot: Smaller lots often require an aerobic system since they release cleaner wastewater.
Local Regulations: Some counties require aerobic systems in certain areas.
Maintenance Needs: If you’re not interested in regular maintenance, an anaerobic system may be the better fit.
How Aerobic Septic Systems Work (And When They’re the Right Choice)
Aerobic septic systems speed up the waste breakdown process by pumping oxygen into the tank. This allows aerobic bacteria to thrive and break down waste more efficiently.
Key Features of Aerobic Systems:
Requires an aeration pump to supply oxygen
Breaks down waste faster and more efficiently
Produces cleaner wastewater (sometimes clean enough for surface irrigation)
Typically requires a smaller drain field
When an Aerobic System Makes Sense:
Your property has poor soil drainage
You have a small lot and need a compact system
You want a more eco-friendly option
Local regulations require one
Potential Downsides:
Higher upfront cost (between $10,000–$20,000)
Requires electricity (power outages can be an issue)
Needs regular maintenance (including pump and filter upkeep)
How Anaerobic Septic Systems Work (And Why Many Homeowners Stick with Them)
Anaerobic systems are the traditional septic system most people are familiar with. They use bacteria that don’t need oxygen to break down waste. The liquid waste then flows into a drain field, where the soil filters out contaminants.
Key Features of Anaerobic Systems:
No electrical components (lower risk of mechanical failure)
Less maintenance (no aeration pump to worry about)
Lower installation cost (between $5,000–$12,000)
When an Anaerobic System Makes Sense:
You have plenty of space for a drain field
Your soil drains well and can handle the outflow
You want a simple, low-maintenance option
You don’t want to worry about electricity or pumps
Potential Downsides:
Slower waste breakdown (can lead to buildup over time)
Requires a larger drain field
Less effective in poor soil conditions
Pros and Cons: Aerobic vs. Anaerobic Septic Systems
Installation Costs:
Aerobic systems cost $10,000–$20,000
Anaerobic systems cost $5,000–$12,000
Maintenance Needs:
Aerobic systems require regular maintenance, including pump and filter upkeep
Anaerobic systems have lower maintenance needs
Power Requirements:
Aerobic systems need electricity
Anaerobic systems don’t require power
Drain Field Size:
Aerobic systems require a smaller drain field
Anaerobic systems need a larger drain field
Lifespan:
Aerobic systems last 20–40 years
Anaerobic systems last 15–30 years
Environmental Impact:
Aerobic systems release cleaner wastewater
Anaerobic systems are less eco-friendly
Local Regulations: What You Need to Know in Olympia & Pierce County
In some areas of Pierce County, especially those with poor soil conditions, local health departments may require an aerobic system. Before making a decision, check with the Thurston or Pierce County Health Department or talk to a professional septic installer (like us) to ensure your system will meet regulations.
Which System Is Right for Your Home? Key Factors to Consider
Here’s a quick checklist to help you decide:
Small lot? → Aerobic
Lots of land? → Anaerobic
Good soil drainage? → Anaerobic
Poor soil? → Aerobic
Want lower maintenance? → Anaerobic
More eco-friendly? → Aerobic
If you’re still unsure, we highly recommend a site evaluation before making a final decision.
Common Mistakes to Avoid When Choosing a Septic System
🚨 Ignoring soil conditions – Your soil type dictates which system works best.
🚨 Choosing based on price alone – Cheaper isn’t always better.
🚨 Not considering maintenance – Some homeowners regret choosing high-maintenance systems.
🚨 Skipping permits – A permit violation can cost you thousands.
Final Thoughts: Our Expert Recommendation for Pierce County Homeowners
So, which system is right for you?
If you want low maintenance and lower upfront costs, an anaerobic system might be the best fit.
If you have poor soil, a small lot, or want a cleaner wastewater output, an aerobic system could be the smarter long-term investment.
Still not sure? We can help. At Southbay Septic & Excavation, we’ve installed both types of systems across Thurston, Pierce, Lewis, and Kitsap Counties—and we’re happy to guide you through the process.
Want a free consultation or have questions? Give us a call today.
