Single Compartment Primary Septic Tanks

A primary septic tank is an underground fiberglass tank consisting of a single tank, multiple tanks, or multiple compartments in one tank.  The first tank or compartment is referred to as the primary.  This tank or compartment receives all the solids and wastewater from the bathrooms, kitchens, and laundry.  The primary tank acts an anaerobic digester, using time to physically separate the waste stream.  This time factor also allows the anaerobic bacteria in the tank to breakdown the waste solids.  In this primary compartment or tank, solids settle to the bottom of the tank to create a sludge layer, while grease, oils, and fats rise to the top layer of the tank to create a scum layer.  The center zone of the tank is the effluent portion of the waste stream, sometimes referred to as the clear zone of the tank.  This clear zone is usually located at the furthest distance from the inlet at approximately 60% of the tank depth, measured from the tank bottom.  Fiberglass Tank Solutions manufacturers primary septic tanks from 500 gallons to 50,000 gallons. 


Single compartment fiberglass septic tank in 3d

Baffled 2-Compartment Septic Tanks

In some tank designs, a baffle can be installed to break this tank into compartments.  Compartmented tanks help retain solids and create cleaner effluent.  These compartments break up the total tank volume into 2/3 and 1/3 tank compartments.  A drop tee is one method that can be utilized as part of the design to remove the clear zone effluent from one compartment to the other.  Another method uses holes located in the baffle.  Both methods allow the clear zone or settled effluent to discharge at the 60% tank volume level.  Fiberglass Tank Solutions can manufacturer combination tanks in 4’ – 12’ diameters with a full family of features to complete these custom designed tanks.

Two compartment septic tank with duplex effluent filters in 3d

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