Like a Pressure Distribution System, the household plumbing collects the wastewater and sends it to the septic tank where it is separated into the three layers : sludge, scum and wastewater.  In a Gravity Distribution System, the effluent from the tank's 2nd chamber (effluent dosing chamber) is delivered to the treatment field by using a syphon or drainline that uses gravity to move the water out of the tank once it reaches a certain level.


Gravity systems have been used for decades, and many are still in place today.   However, due to new regulations and advances in technology, most modern installations do not use gravity systems.  Gravity systems generally require a larger footprint for the treatment field.  They are prone to overloading zones and not distributing effluent equally throughout the treatment field.  


Most gravity systems will consist of a standard 2 compartment septic tank and a buried treatment field.  4" perforated sewer pipe is laid in drainrock in trenches and covered over.   Some may argue that a gravity system is less expensive than a pressure system.  While it is true that most gravity system configurations require less components and materials, the excavation costs are much higher due to larger field requirements.   Our designs take into account all factors and provide you with the best solution.


Hybrid systems can also be designed where a pump (pressurized) in the tank pumps the water to a distribution box in the field, and from the distribution box to weeping lateral trenches the effluent is distributed by gravity.  

Typical 2 chamber septic tank
Gravity Distribution
Gravity distribution
Gravity distribution
Typical Tank and Field
BBB - Septic System Design, Septic System Installation and Service

#19 SITE 10 RR1




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