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Types of Septic Systems


 Each property in the County is served by either the WSSC public sewer system or a private septic system.  There are 30,000 to 40,000 properties served by septic systems in Montgomery County.

Types of septic systems

There are several types of conventional septic systems that may be approvable for installation to serve a new or existing structure in the County.  The types of conventional septic systems include: drywells (seepage pits), deep or shallow trenches and conventional sandmounds. 

There are also several types of non-conventional septic systems that may be approvable for installaton to fix a failing septic system only.  Properties served by these types of systems are not eligible for building permit approvals that include living space.

Please refer to our Guideline for Septic System Repairs for more information on the process of installing a new septic system to fix a failing condition. 

Drywells

The drywell is a type of septic system that is generally suitable only in ideal soil conditions.  Installation of a drywell system is advantagous especially in situations where there is little available square footage for  the septic system.  The drywell was the type of septic system most commonly installed to serve homes built in the 1940's thru the 1960's.  The drywell is a cylindrical structure ususally no more than fifteen (15) feet deep and twelve (12) feet in diameter.  The structure is constructed of either staggered cinder blocks or cement well rings with clean gravel added to the interior and exterior of the walls.  Drywells are installed entirely below the ground surface.

Trenches

Deep or shallow trench systems are currently the most commonly installed type of septic system in the County.  The design specifications (depth and linear footage) of a trench system are determined by percolation test results and topography.  Trenches are usually two or three feet in width, with varying depth and stone volume.  Perforated pipe is placed in the trenches to allow transport of sewage effluent into the trenches and to the soil for proper filtration.  Trenches are installed entirely below the ground surface.

Conventional sandmounds

Sandmound septic systems are a type of septic system that are paritally above the ground surface.  Please refer to our Sandmound guideline for more information.

Non-conventional septic systems

There are several types of non-conventional septic systems that may be approved for installation to replace a failing septic system serving an existing dwelling.  These types of septic systems are not approvable for use in any situation related to a building permit for new construction.  Please refer to our Non-conventional septic systems guideline for more information.

Other Agencies and Utilities to Contact  
   
  Maryland Department of Assessments and Taxation
  Maryland Department of the Environment