Septic System

Where no city sewer line reaches, a home must treat its own wastewater underground. That is what a septic system does. It works as a self-contained sewer for a single property. The U.S. EPA describes the basic design. Every drain in the house flows to a buried, watertight septic tank. Solids settle to the bottom as sludge, and grease floats to the top as scum. The clearer liquid in the middle flows out to a leach field, also called a drainfield, where it soaks slowly into the soil and natural filtering finishes the job.

In the Phoenix metro, septic is the norm for rural custom homes. That means Rio Verde Foothills, the desert north of Cave Creek, much of unincorporated Maricopa County, and parts of Pinal County near Apache Junction and Casa Grande. If your lot has no sewer at the street, you build a septic system. It is a permitted, engineered part of the home, not an afterthought.

Two Arizona rules drive the design. First, you usually need a percolation test or soil evaluation to prove the ground absorbs water well enough for a leach field. Slow-draining or expansive soil can force a larger field, or an engineered alternative system that costs more. Second, the county environmental health office permits the install, either Maricopa County Environmental Services or Pinal County, and inspects it before backfill.

Take a Rio Verde owner on a five-acre parcel. A conventional tank-and-leach-field system might run $15,000 to $35,000 or more. The figure climbs if the perc test calls for an engineered design or a bigger field.

Septic shapes other site choices too. State and county rules set minimum distances between the system and any well, property line, or wash. So the septic location, the well, and the home footprint all get planned together, well before you set the foundation.