How conventional systems work
Wastewater flows from the house into a 2-compartment concrete tank. Solids settle, scum floats, and the clear middle layer flows out to a gravity drain field where soil microbes finish treatment.
Cheap, simple, very low maintenance — but only legal where soil percolation and lot size allow.
How aerobic systems work
A trash tank, a treatment tank with an air pump, and a pump tank that sprays treated effluent across a designated lawn area. The aeration produces near-clear effluent that can be discharged on the surface.
Required by most Houston-area counties on small lots, clay soil, or high water tables — which is most of the metro.
Choosing between them
Lot under 1 acre or clay-heavy: aerobic, almost always.
Acreage with sandy/loamy soil: conventional if your soil test passes.
Budget-driven new build: conventional is $3K–$5K cheaper but only if your lot qualifies.
Already on aerobic: keep up the quarterly maintenance contract — it's required by Texas law.