Alternating Gravity System:    ***Pictures Below***

Generally, when a conventional gravity septic system is designed, you will have a septic tank, a gravity flow transport pipe with transfers effluent (wastewater) to the gravity drain field.  Usually, a "reserve" area is designated on the property to potentially allow a new drain field to be installed in the event that the existing drain field fails.  Health department approval would be needed to install this reserve area.  With the installation of an alternating gravity septic system, you will have both drain field's installed at time of original installation.  The alternating type system will either be an in-ground (at grade) or raised gravity mound system.  Site conditions determine which type of alternating gravity system is needed.  Sometimes a pump tank is needed after the septic tank to deliver the effluent to the gravity drain field.

The drain field's should get switched, or alternated every year.  The homeowner or licensed septic professional would alternate between the two drain field's by means of a diverter valve (see picture below).  There are two basic types of diverter valves as pictured below.   During original installation, the licensed installer should instruct the homeowner on how to properly alternate the drain fields.

Below are some pictures of typical alternating gravity drain fields:



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