Tank Requirements


An amendment to Chapter 1066 of the county’s codified ordinances addresses the structural soundness and water tightness of tanks used for on-site sewage systems.

To further address soundness and water tightness, the Health Department will observe either a water test or a vacuum test at the time of the construction inspection.

Structural Soundness Tank Requirements

  • Burial depth will be limited to 4 feet
  • Manufacturers will be required to have their engineer certify that the design can meet all reasonably expected loading conditions, including:
    • Burial depth
    • Empty tank installed with water table at top of ground
    • Tank full to top of riser
    • Vehicular traffic and any other reasonable expected loading conditions
  • The manufacturer will have to certify that all tanks manufactured meet the engineer design

In locating the tanks on site, they shall not be placed in low areas or swales subject to drainage, channeling of rainfall, or ponding of water. Tanks shall be protected with controlled backfill when shrink-swell soil is present. If water table indications are observed or measured above penetrations or lank seams, a water table reduction system must be installed to lower the water table below the seam or penetration.

Accepted Tanks List

The Loudoun County Health Department has developed the Loudoun On-Site Wastewater Tank Structural Requirements (PDF) to provide more detail to manufacturers. View a list of accepted tanks (PDF).

Water Tightness Tank Requirements

  • All tank lids shall be manufactured with risers pre-cast into the top of the tank
  • Boots for all tanks must meet ASTM C-923
  • Boots for concrete tanks must meet ASTM C-923 and have a clamp assembly to resist pipe deformation
  • Manufacturers shall install watertight boots at all penetrations
  • Risers shall terminate a maximum of 6 inches below finished grade

Contact Information

Additional information can be obtained by contacting the Health Department at 703-777-0234 or by emailing our office.