Why an Intermittent Sand Filter?

Prior to the Spring of 2002, that question was a lot easier to answer. Where high groundwater, poor soils, bedrock, or other site constraints rule out a conventional septic system, the Anchorage Tank Intermittent Sand Filter (ISF) once was the ideal solution. With the introduction of Orenco's AdvanTex Treatment Systems, the Sand Filter has been rendered practically obsolete in many situations. Once you browse the AdvanTex section of this web site and compare, it is easy to see why the Sand Filter may no longer be the best choice. This section of our online catalog remains as a support to the hundreds of existing Sand Filter systems already installed.

Although Intermittent Sand Filters will no longer be stocked by Anchorage Tank, the systems are still available as a special order.

System Operation Concept

Raw sewage from the house enters the septic tank, most often a S.T.E.P. tank. Grease floats to the surface and slowly digested solids sink, forming a sludge layer at the bottom of the tank. Easily digested solids are broken down by microorganisms and are biologically changed to liquids and gasses. When the liquid in the tank reaches a predetermined level, it is pumped from the tank to pressurize the distribution manifold on the top of the sand filter bed.

Evenly spread over the surface of the bed, the effluent percolates through the sand, where naturally occurring microorganisms clinging to sand particles organically break down contaminants.

In the bottom of the sand filter, the treated effluent - now clear and odorless - can go to one of two places. In a bottomless sand filter, it simply percolates further downward into the native soil. In a gravity discharge sand filter, there is a liner throughout the filter. Effluent is collected in a slotted underdrain pipe and flows into a reduced size drainfield.