Updated 5 October 2026
Read This Before Getting a Quote
Many states and counties require a service contract on an aerobic treatment unit, at least for the first years, and owners commonly keep one for the life of the system. At our estimate of $200-$400 a year, that is $4,000-$8,000 over 20 years on top of the installation cost. Most installer quotes do not include this ongoing obligation. Before accepting any ATU quote, ask: what is the annual service contract cost, who provides it, and is it legally required in my county?
An aerobic treatment unit (ATU) uses oxygen injection to treat wastewater to near-secondary standards - significantly cleaner than a conventional septic tank. This allows a much smaller drain field and makes ATUs permissible in locations where conventional and mound systems cannot be permitted. They are required or commonly used in failed-perc situations, high-water-table coastal sites, environmentally sensitive zones, and small lots in states like Texas and Florida where ATUs are a primary alternative to conventional systems.
Wastewater enters a pretreatment trash tank that separates large solids. Effluent then flows to the aeration chamber, where an electric aerator (air pump) continuously injects oxygen. The oxygen supports a dense population of aerobic bacteria that break down organic waste far more efficiently than the anaerobic bacteria in a conventional tank.
After aeration, the treated effluent flows to a clarifier chamber where residual suspended solids settle. Most state codes then require disinfection - either chlorine tablet feeders or UV disinfection - before the treated effluent is dispersed to a small drain field or, in some states, spray-irrigated on the surface. The treated effluent from a properly functioning ATU typically meets or exceeds secondary treatment standards.
| Line Item | Low | Typical | High |
|---|---|---|---|
| ATU unit (tank + aerator) | $4,000 | $7,000 | $10,000 |
| Engineered design (mandatory) | $1,500 | $2,500 | $3,500 |
| Permits and inspection fees | $500 | $1,000 | $1,500 |
| Electrical hookup | $500 | $900 | $1,500 |
| Small drain field installation | $1,500 | $2,500 | $4,000 |
| Installation and excavation labor | $3,000 | $5,000 | $8,000 |
| Disinfection system (chlorine/UV) | $300 | $600 | $1,000 |
| Total installed | $11,300 | $19,500 | $29,500 |
| Annual service contract (ongoing) | $200/yr | $300/yr | $400/yr |
| Electricity (aerator) | $150/yr | $225/yr | $300/yr |
| 20-year total cost of ownership | $19,800 | $33,500 | $51,500 |
20-year TCO includes install + 20 annual service contracts + 20 years electricity + 2 pump replacements (~$800 each). Does not include tank pump-outs ($300-$500 every 1-2 years).
Rules differ by state and often by county, so confirm yours before budgeting. One verified example: Texas requires a two-year initial service policy on every aerobic system, with testing at least once every four months (twice a year with electronic monitoring). After two years, the owner of a single-family home may renew a maintenance contract or maintain the system personally, unless the county order requires a contract (30 TAC 285.7 and 285.91).
Elsewhere the requirement may sit in state rule, county rule, or the manufacturer approval. Always confirm with your county health department before budget planning.
| Brand | Unit Cost |
|---|---|
| Norweco Singulair | $5,000-$8,000 |
| Hoot Aerobic | $4,000-$7,000 |
| Jet Inc. | $4,500-$8,000 |
| AquaSafe | $5,000-$9,000 |
Reader Questions
Send the question over. A person reads each one, and the answer names the source it leans on, whether that is a state code, a county fee schedule or a published installer range. If your question turns out to be one plenty of people on rural lots are asking, we will ask you first, then put an anonymised version up here.
What this is not. A cost reference, not a design, engineering or permitting decision. The percolation result, the system sizing and the permit itself sit with your county health department and a licensed installer who has walked the lot.
Updated 2026-04-27