The two main septic system types installed in the DFW Metroplex are conventional gravity systems and aerobic treatment units (ATUs). Each has clear advantages — and your soil and county usually decide for you.
Conventional (anaerobic) septic systems
A conventional system is a sealed tank where solids settle and anaerobic bacteria slowly break them down. Liquid effluent flows out into a gravel-and-pipe drain field for final treatment by the soil.
These systems have no moving parts, no electricity, and last 30+ years with routine pumping. They're the lowest cost to install ($5,000–$10,000 in DFW) when soil and lot size allow.
Aerobic treatment units (ATUs)
An ATU injects oxygen into the tank, supercharging bacterial breakdown. The effluent that leaves an aerobic tank is far cleaner than conventional output — clean enough to surface-dispose via spray heads after chlorination.
ATUs are required when soil won't perc, when the lot is too small for a conventional field, or when county code specifies them. Most of Collin County and big sections of Denton and Dallas counties fall into this bucket because of black-gumbo clay.
Side-by-side comparison
Install cost: Conventional $5,000–$10,000 · Aerobic $8,000–$18,000
Lot size needed: Conventional ~1 acre · Aerobic 0.5 acre or less
Soil tolerance: Conventional needs permeable soil · Aerobic works in clay
Electricity required: No · Yes
Pumping interval: 3–5 years · 2–3 years (plus quarterly maintenance)
Mandatory maintenance contract: No · Yes (Texas rule)
Lifespan (tank): 40+ years · 30+ years
Lifespan (mechanical parts): n/a · Pump and aerator 10–15 years
How DFW counties decide for you
TCEQ delegates OSSF permitting to county designated representatives. In practice: Collin County rarely permits new conventional systems on lots under 1 acre. Denton, Rockwall, and most of Dallas County evaluate soil case-by-case. Tarrant and Parker counties more often allow conventional systems thanks to better-draining soils.
Which one is right for you?
Pick conventional if your soil perms well, you have at least an acre, and you want the lowest total cost of ownership.
Pick aerobic if your soil is clay, your lot is tight, your county requires it, or you simply want cleaner effluent dispersal.
The soil evaluation is the deciding factor. Don't budget for one system type until the perc test is done.
Frequently Asked Questions
Are aerobic systems more reliable than conventional?+
Not inherently. They produce cleaner effluent but have pumps, aerators, and control panels that fail. Conventional systems are simpler and have fewer failure modes.
Can I convert a conventional system to aerobic?+
Yes, but it usually requires a new tank, electrical service, and a new dispersal field. Often the economics only make sense if the original system has failed.
Do aerobic systems smell?+
A properly running ATU should not produce odor. Persistent smells almost always mean the aerator or chlorinator has failed.
Which is better for resale value in DFW?+
Either is fine as long as it's maintained and passes inspection. Real-estate buyers care more about the maintenance log than the system type.