Frequently Asked Questions on Septic Systems

The Department of Environmental Health and Quality and the California Regional Water Quality Control Board consider the combination of a septic tank connected to leach lines (with gravel and pipe or plastic chambers), horizontal seepage pits, or vertical seepage pits as conventional septic system design applications. Leach lines can be installed anywhere in the county where the site meets design criteria. Vertical seepage pits are restricted to coastal sedimentary basins where groundwater is degraded by salt-water intrusion. Horizontal seepage pits are restricted to sites that have deep, permeable soil, with uniform good percolation rates. All septic system designs are required to meet the Regional Water Quality Control Board's (RWQCB) requirement of at least 5 feet of separation between anticipated high groundwater levels and the bottom of the disposal system.

Supplemental Treatment Systems (OWTS-STS's) offer higher treatment than a standard conventional system and can reduce the separation required between the treatment system and high groundwater to 2 feet. As of Aug 2015, the County of San Diego adopted the Local Area Management Plan (LAMP) in agreement from the RWQCB.  The LAMP allows OWTS-STS's to be used for the purposes of developing existing undeveloped lots and creating new lots with parcel and subdivision maps.

Groundwater is a resource for drinking water and the sole source of drinking water in many rural San Diego communities. Septic systems can be a source of contamination to groundwater. Conversely, groundwater can also cause a septic system to fail from both soil saturation, and groundwater intrusion into the septic system. Conventional septic systems must have at least 5 feet of unsaturated soil depth for the soil to provide treatment to the sewage effluent being discharged from the septic tank to the disposal field.  For these reasons, a minimum separation of no less than 5 feet must be maintained from the bottom of the sewage disposal system and the highest anticipated groundwater levels at the conventional disposal system location. Supplemental Treatment Systems must have at least 2 feet of unsaturated soil.  Numerous factors within a watershed basin affect the depth to groundwater, including development, agricultural use, soil depth, soil permeability, the amount of surface flow into the basin, and the rate water flows out of the basin in addition to rainfall. 

The DEHQ Land and Water Quality Division office located in San Diego at 5500 Overland Ave, Suite 210; maintain records of septic systems that have been installed since the late 1970's. These are filed by the tax assessor parcel number. The phone number for the San Diego office is (858) 565-5173.

The installation or modification of any septic system within the county of San Diego, including all incorporated cities will be within the jurisdiction of the Department of Environmental Health and Quality. The property owner can obtain a septic tank permit for installing a septic system on his or her property. In all other situations a licensed C-36, C-42, Class A, or Class B contractor would be required to obtain permits to install a septic system. 

For septic systems serving private residences, the size of the disposal field is a combination of percolation test data and the number of bedrooms within each dwelling unit. Septic tanks are sized according to the number of bedrooms.

For commercial designs, the size of the disposal field is a combination of percolation test data and the peak daily sewage flows based on the type of usage and occupancy of the site. Septic tank sizes are also based on the peak daily sewage flow.

Licensed civil engineers, registered geologists, and registered environmental health specialists are currently recognized to be qualified to design septic systems.