When you build a barndominium on a rural lot, one of the most critical yet often overlooked systems is the septic system. Unlike urban homes connected to city sewer lines, most rural barndominiums require an independent, on-site wastewater solution.
Getting your septic system right is vital—not just for comfort and sanitation, but for code compliance, environmental protection, and long-term durability. In this blog post, we’ll walk you through how to plan, design, and install a septic system that fits your barndominium and your land.
Why Barndominiums Need Special Septic Consideration
Barndominiums are frequently built on large, undeveloped parcels of land, sometimes far from utility infrastructure. While this gives you freedom and privacy, it also means you’ll need to think carefully about:
- Soil conditions and perc testing
- Local health department regulations
- Water usage based on household size
- Topography and drainage
- Future expansion or accessory buildings
Designing your septic system isn’t just about digging a tank and laying some pipe—it’s about customizing a solution that fits your home’s unique usage patterns and the land’s physical characteristics.
Step 1: Understand How a Septic System Works
Before we get into design specifics, it helps to understand the basic components of a conventional septic system:
- Septic Tank
This watertight tank receives all wastewater from your home. Solids settle at the bottom (sludge), lighter materials float to the top (scum), and the liquid in the middle (effluent) flows out to the drain field.
- Distribution Box
Effluent from the septic tank flows into a distribution box that evenly channels it into the drain field pipes.
- Drain Field (Leach Field)
This is where the final treatment occurs. Effluent is filtered through gravel and soil, where microbes break down contaminants before it returns to the groundwater.
Some properties may require advanced systems, including aerobic treatment units or mound systems, if the land doesn’t support a traditional gravity-fed system.
Step 2: Conduct a Percolation (Perc) Test
A perc test measures how quickly water drains through your soil. It’s usually performed by a licensed soil engineer or technician and is required before obtaining a septic permit in most areas.
What the Perc Test Tells You:
- Soil composition (clay, loam, sand)
- Water absorption rate
- Seasonal water table levels
- Suitability of land for a drain field
Poor Perc Rate?
If your soil drains too slowly or too quickly, you may need:
- A larger drain field
- An engineered system (e.g., sand filter or mound)
- Soil amendments to meet code requirements
Pro tip: Do this before you finalize your barndominium site plan, as the soil can limit your layout options.
Step 3: Estimate System Size Based on Usage
Septic system size isn’t based on square footage—it’s based on the number of bedrooms and anticipated daily wastewater flow.
Typical Sizing Guidelines:
| Bedrooms | Minimum Tank Size |
| 1–2 | 750–1,000 gallons |
| 3 | 1,000–1,250 gallons |
| 4 | 1,250–1,500 gallons |
| 5+ | 1,500+ gallons |
If you plan to have a:
- Home office or workshop with plumbing
- Guest suite or mother-in-law unit
- Laundry-heavy household
…you may need a larger tank or dual systems. Always plan for future expansion, especially with barndominiums that grow over time.
Step 4: Plan Septic Layout Based on Topography
Once you’ve got the perc test results and usage estimates, the next step is integrating the septic system into your site plan.
Key Considerations:
- Slope: Drain fields must be laid on relatively flat terrain or designed to handle elevation changes.
- Distance from well: Must be at least 50–100 feet away, depending on local regulations.
- Distance from structure: Generally 10–20 feet from the house.
- Access for maintenance: Don’t bury the tank too deep or place it under patios, driveways, or heavy structures.
Barndominium Tip:
If your barndominium includes a large shop or garage, keep the septic system away from heavy equipment or parking areas to prevent soil compaction.
Step 5: Choose the Right Type of Septic System
There’s no one-size-fits-all. Your soil, lot layout, and local code will help determine the right system:
- Conventional Gravity System
- Uses gravity to move wastewater
- Least expensive and easiest to maintain
- Requires good soil and topography
- Pressure Distribution System
- Uses a pump to evenly distribute effluent
- Better for uneven or shallow soils
- Mound System
- Used when soil depth or permeability is poor
- Wastewater is treated in an above-ground sand mound
- Aerobic Treatment Unit (ATU)
- Introduces oxygen to promote faster breakdown
- More efficient, but more expensive and maintenance-intensive
- Recirculating Sand Filter
- Compact and high-performance
- Suitable for environmentally sensitive lots or poor soils
Discuss your options with a licensed septic designer or your local health department to choose the system that best fits your lot.
Step 6: Navigate Permits and Inspections
Every state—and often, every county—has different regulations for septic system design and installation.
Expect to Provide:
- Perc test results
- Detailed site and plumbing plans
- Usage calculations
- Proof of licensed installer or engineer
Inspection Stages May Include:
- Perc test verification
- Excavation and trench inspections
- Final installation sign-off before backfilling
Never skip permitting—non-compliant systems can result in fines, forced removal, and legal headaches during resale.
Step 7: Plan for Long-Term Maintenance
Like any part of your barndominium, your septic system needs care.
General Maintenance Tips:
- Pump the tank every 3–5 years
- Avoid harsh chemicals, bleach, or antibacterial soaps
- Don’t plant trees over drain fields
- Use water-efficient appliances
- Monitor for signs of failure (slow drains, soggy soil, odors)
You might also consider adding a septic riser, which brings the tank access to ground level and makes pumping and inspection much easier.
Bonus Tip: Think Green and Sustainable
If you’re going off-grid or building a sustainable barndominium, consider greywater reuse systems that divert sink, shower, or laundry water for irrigation, reducing load on your septic system.
Also, low-flow toilets, faucet aerators, and efficient dishwashers can reduce water use and prolong the life of your system.
Final Thoughts
Designing a septic system for your barndominium may not be the flashiest part of the build—but it’s one of the most foundational. A well-planned system ensures comfort, protects your land, and keeps your home code-compliant.
By starting early, working with local experts, and understanding your land’s limitations and potential, you can create a septic solution that supports your barndominium lifestyle for decades to come.