California Laws on Septic Tanks

Some homeowners in rural areas have to install on-site wastewater treatment systems, known as septic tanks, because they cannot connect to main sewage systems. Before you install a septic tank in California, make sure you're familiar with the rules. In 2012, the California State Board amended septic tank installation regulations to correct and prevent system failures caused by poor siting and design.

California septic tank laws classify septic tanks according to a tier system. A state-licensed contractor performs an evaluation to determine the correct tier for an existing system or proposed site:

Tier 0 refers to existing septic systems up to 10,000 gallons per day of projected flow, which are in a good state of repair and pose no known threat to local water supplies or to the environment.

Tier 1 septic systems are new or replacement systems in low-risk areas with no Local Agency Management Program and up to 3,500 gallons per day of projected flow.

Tier 2 areas have Local Agency Management Programs, pose a moderate risk profile for new and replacement septic tank systems and have up to 10,000 gallons per day of projected flow.

Tier 3 installation requirements apply when nearby bodies of water – those less than 600 feet away – are polluted or contaminated.

Tier 4 is for existing septic systems in a state of disrepair or those causing environmental damage due to effluent seepage or runoff. Tier 4 systems require corrective action, incur higher costs and are subject to the most government restrictions.

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Septic tank systems installed before the revised California septic system regulations came into force are generally not affected by the policy amendments. If they are classed as Tier 0 and are in a good state of repair and pose no known threat to local water supplies or to the environment, homeowners can continue to use them as before without making any changes.

In California, a homeowner must obtain a septic tank permit from the California State Water Board before installing a septic system on his property. The first step is a site evaluation by a state-licensed contractor. Septic systems must be installed by either a qualified professional or by the homeowner, and must pass inspection by the water board before use. Residential septic tanks are sized according to the number of bedrooms in the property.

All septic tank owners must keep their septic systems in good working condition, including inspection and pumping of solids as necessary. Removing accumulated solid residues before they transfer into the leach field is the most important step in maintaining a trouble-free septic system.

A septic tank inspection typically costs between $100 and $200. A residential septic system should be pumped every one to five years depending on the size of the household and the amount of solid waste produced. The cost varies accordingly, but is typically in the region of $300 to $500. Your tank must be uncovered to be inspected and pumped out. You can do this yourself or pay the pumper to do it.

To avoid fines for illegal septic systems, California homeowners should consider installing an aerobic system to extend the useful life of the septic tank and fix a number of septic tank problems before they cause complete system failure. A septic aerator boosts the efficiency of the in-tank decomposition process and reduces the risks of environmental damage from runoff, seepage or surface effluent dispersal.

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