Not every septic system at the lake works the same way, and knowing which type you have changes what maintenance you actually need. Here’s how to tell the difference, and why it matters more here than in most parts of Missouri.
Conventional Gravity Systems
A conventional system relies on gravity and natural settling: wastewater flows into a tank, solids settle to the bottom while liquid flows out to a drain field, where soil does the final filtering. There’s no motor, no electricity, and no moving parts — which means less that can break, but also fewer options for tight or difficult lots, since it needs enough usable land for the drain field to work properly.
Aeration (ATU) Systems
An aeration treatment unit adds a motor that pumps air into the tank, speeding up the breakdown of waste before it reaches the drain field. This produces more thoroughly treated effluent, which is often required — not just preferred — on lots close to the shoreline where a conventional system’s setback requirements can’t be met. The tradeoff is a genuinely mechanical system: a running motor, an electrical connection, and typically a required ongoing service contract with a certified maintenance provider as a condition of the operating permit.
How to Tell Which One You Have
- Check for a control panel or alarm box. Aeration systems have an electrical control panel, usually mounted on an exterior wall or a post near the tank, with a light or alarm that indicates system status. A conventional system has no such panel.
- Listen near the tank access point. A running aeration motor produces a faint, continuous hum. A conventional tank is silent.
- Check your property’s location. Aeration systems are far more common on tight, close-to-shoreline lots — Sunrise Beach’s west lakefront has the highest concentration in our service area, largely due to narrow lots and setback rules. Inland acreage properties, more common around Camdenton and Eldon, are more likely to be conventional.
- Check your permit records, if available. The system type is typically specified on the original installation permit.
Why the Distinction Matters
If you have an aeration system, confirming an active maintenance contract is in place should be a near-immediate priority if you’re not sure — it’s often a permit requirement, not just a recommendation, and a lapsed contract can mean the system isn’t actually treating wastewater properly even if it looks like it’s running. See our aeration service page → for what that involves. If you have a conventional system, your main maintenance focus is simpler: staying on a regular pumping schedule. See our pumping service →
Cost Differences Between the Two
Aeration systems generally cost more to maintain over time than conventional systems, simply because there’s more to maintain — a motor, an electrical connection, and a required service contract, on top of the periodic pumping both system types need. Conventional systems have lower ongoing costs but less flexibility about where they can be installed. Neither system is inherently “better” outside the context of your specific lot; the choice (when there is one) usually comes down to what your soil, grade, and shoreline setback actually allow, not personal preference.
If You’re Buying a Property and Don’t Know Which Type It Has
This comes up constantly in lake real estate transactions, and it’s a reasonable thing to ask about before you’re deep into a purchase decision. A real estate inspection will identify the system type as a matter of course, along with its condition — worth requesting even if the listing doesn’t specify, since sellers don’t always know the technical details of what’s already on the property either.
Frequently Asked Questions
Can I convert a conventional system to an aeration system, or vice versa?
Technically yes, but it’s a significant project involving permitting and design work, not a simple retrofit — generally only done when required by new construction, a failed system, or a change in shoreline setback compliance.
Do aeration systems need to be pumped like conventional tanks?
Yes, aeration systems still need periodic pumping in addition to their separate motor and mechanical maintenance — the aeration process doesn’t eliminate the need to remove accumulated solids.
