Understanding Your Septic Options (and How We Ended Up with a Lagoon)
- Dani
- Jun 15
- 3 min read
Before we got into this process, I honestly thought a “septic system” was just one thing you install and move on. Turns out, there are actually several different types—and which one you can use depends almost entirely on your land.
When you’re building on rural property, your soil test (perc test), groundwater levels, lot size, and county regulations all play a role in what’s even allowed.
Conventional Septic System
The most common option is a conventional septic system, which uses a tank and an underground drain field. This works when your soil absorbs water at a steady rate and there’s enough usable space for the system to spread out underground.
Aerobic System
If your soil doesn’t meet those conditions, you might be directed toward an aerobic system, which uses oxygen and mechanical components to treat wastewater more intensively before releasing it into a smaller drain field.
These systems can work on more challenging lots, but they require more maintenance and ongoing upkeep.
Mound System
Another option is a mound system, which is used when the soil is too shallow, too rocky, or when groundwater levels are too high. Instead of digging down, the drain field is built up above ground in a raised mound that allows proper filtration.
Lagoon System (What We Ended Up With)
And then there’s the lagoon system, which is what we ended up with.
A lagoon is a large, shallow pond that treats wastewater naturally through evaporation,
sunlight, and oxygen.
Once we completed our soil testing and met with the county health department, it became clear that a conventional system wasn’t the right fit for our property. Based on our soil conditions, required setbacks, and overall site layout, the county walked us through the options that were actually approved for our land.
In our case, that left us with a lagoon as the most practical and approved solution.
One of the biggest things we learned through all of this is that you don’t really “choose” your septic system first—your land and local regulations determine what’s possible, and then you work within those options.
What Our Septic System Cost
One of the biggest questions we had going into this process was simple: how much is this actually going to cost?
For our property in rural Missouri, our lagoon septic system came out to $7,250.
From what we’ve learned, that is pretty normal for our area. Costs can swing a lot depending on soil conditions, lot layout, and how much work has to be done to prepare the site.
Here’s a general breakdown of what that cost typically includes:
County permitting and inspections: ~$200–$500
Soil testing / site evaluation coordination: ~$300–$800 (if not already done separately)
Excavation and grading for lagoon: ~$2,000–$3,000
Liner and lagoon construction materials: ~$1,000–$2,000
Plumbing lines from house to system: ~$800–$1,500
Final grading and system setup: ~$500–$1,000
Every property is different, so these numbers aren’t exact—but they give a realistic idea of where the money goes.
One thing we didn’t expect was how much the land itself affects the price. If your property
needs extra grading, has difficult soil, or requires a more complex layout, costs can increase quickly.
In our case, we didn’t have any major surprises or extreme site work, which helped keep our total on the lower end of the typical range.
Looking back, this was one of those parts of building on raw land that we completely underestimated at first. It’s not just “installing a septic system”—it’s preparing the land, working within county requirements, and making sure everything aligns with your well and home layout.
Final Thoughts
The biggest takeaway from all of this is simple: your land makes a lot of the decisions for you when it comes to your build. Although you can't be too picky when land pops up on the market, definitely be thinking about the logistics of it going into it!
If you’re in the middle of this process, just know this part feels confusing for everyone at the start. The good news is, once you understand how it works, you can start making decisions with a lot more confidence—and everything else (well, septic, home placement) starts to fall into place.
If you're looking for more resources about the foundational parts like soil testing, grading, easements, and well water, check out my other blog posts. It's the toolkit I wish I had going into it, and I hope it can help other families on the same journey!
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