Types of Septic Systems in Oregon

"Septic system" covers a surprising range of designs. Two neighboring homes in the Rogue Valley can have completely different systems, one a simple gravity layout from decades ago and the other an engineered treatment unit with a control panel and a service contract. Knowing which type you have tells you how it should be maintained, what can go wrong, and what Oregon requires of you as the owner.

How to find out what you have

Start with DEQ's onsite records for your parcel, searchable by parcel number for Jackson, Josephine and Curry counties. Permits usually name the system type. Clues in the yard help too: a control panel or alarm box on the house or a post suggests a pump or treatment unit; a second tank or a large sealed box suggests a sand filter or ATT. See our guide to finding septic records.

Standard gravity systems

The classic design: wastewater flows downhill from the house to a septic tank, and clarified effluent flows by gravity from the tank, often through a distribution box, into perforated pipe in gravel trenches. There are no pumps or electrical parts. These systems are the simplest to own, and DEQ's homeowner guide recommends inspecting typical gravity systems at least every three years and pumping when sludge and scum measurements say it is due.

What fails: outlet baffles corrode, distribution boxes tip so one trench gets most of the flow, roots enter pipes, and drainfields clog with solids if the tank is neglected.

Pump-to-gravity (effluent pump) systems

When the drainfield is uphill from the tank, a pump chamber collects effluent and a pump lifts it to the field. These systems add a pump, floats, a control panel and a high-water alarm. They are common on Rogue Valley hillsides. Keep the alarm working, and know where the breaker is. See what to do when a septic alarm goes off.

Pressure distribution systems

Instead of letting effluent trickle into one end of a trench, a pump doses small pipes with drilled holes under pressure so effluent spreads evenly across the whole field. This suits shallow or sloping soils. According to DEQ's current operation and maintenance fact sheet, owners of pressurized distribution systems permitted after January 1, 2014 must keep a contract with a certified maintenance provider and have the system inspected at least annually.

Sand filters and recirculating gravel filters

A sand filter adds a lined bed of specified sand between the septic tank and the drainfield. Effluent is dosed onto the sand, where it receives additional treatment before going to the soil. Recirculating gravel filters work on a similar principle with recirculation. DEQ's fact sheet lists residential sand filters permitted after January 1, 2014, commercial sand filters permitted after March 1, 2005, and recirculating gravel filters among the systems that require a maintenance contract and at least annual inspection. DEQ's homeowner guide recommends yearly inspection of sand filter systems.

Alternative treatment technology (ATT)

ATT systems are manufactured treatment units approved by DEQ, such as packed-bed textile filters and aerobic treatment units. They produce cleaner effluent than a septic tank alone, which can allow a system on lots where soil, setbacks or size would rule out a conventional design. Under OAR 340-071-0345, ATT owners must keep a service contract with a maintenance provider certified by the manufacturer, from before installation until the system is decommissioned. More on our ATT maintenance page.

Holding tanks

A holding tank stores wastewater for pumping and hauling, with no drainfield. They are used only in limited situations and need frequent pumping. If a property you are buying has one, ask why and how often it is pumped.

At a glance

Summarized from DEQ's 2024 O&M fact sheet and rules. Confirm requirements for your specific permit with DEQ.

Common questions