California Composting Toilet Laws: What Homeowners, Builders, and Off-Grid Dreamers

Dreaming of ditching the septic tank or sewer for a composting toilet in California? You’re not alone. Composting toilets are a popular choice for off-grid cabins, tiny homes, and even sustainable city projects. But California’s patchwork of state and local rules can leave folks scratching their heads: Are composting toilets actually legal in California? If so, what’s required? Let’s dig into the real-world details, so you can plan your project with confidence (and keep the inspectors happy).

Are Composting Toilets Legal in California?

Yes, composting toilets are legal in California, but you can’t just build any system you want and expect a green light. The law is all about public health, sanitation, and environmental protection. If you want your composting toilet to pass muster for code compliance, insurance, or resale, you’ll need to follow state guidelines and (just as importantly) local codes and health department rules.

Who Makes the Rules?

The California Department of Public Health (CDPH) sets statewide public health rules, but most building codes and septic requirements are adopted, enforced, and sometimes expanded by each county. Cities, counties, and sometimes even special districts may have their own building departments and environmental health divisions. So, while there are state-level standards, local approval is always required.

What Does California Law Say About Composting Toilets?

California’s building code (the California Plumbing Code) includes composting toilets as an approved alternative to standard flush toilets. But here’s what that really means:

Composting toilets must be listed or certified: Most counties require a composting toilet system that’s certified to NSF/ANSI Standard 41 (the national performance/safety standard for composting toilets). Homemade and DIY bucket toilets rarely get approved unless you can prove they meet the same standard.
Permits and inspections are required: Installing a composting toilet as part of a permitted house, accessory dwelling unit, or commercial building always requires permits, and often an inspection.
Composting toilets can’t discharge to ground or water: Composting toilets must safely contain and treat waste; you cannot pipe liquids or solids onto the ground, into a creek, or anywhere else except approved disposal locations.
Greywater must be handled separately: Even if you have a composting toilet, you still need an approved system for greywater (wastewater from sinks, showers, and laundry). California has specific codes for greywater systems (Title 24, Part 5), but direct discharge to land or surface water is illegal unless permitted as a legal greywater system.

When Are Composting Toilets Allowed?

Composting toilets are more likely to be approved in these situations:

Remote/rural properties where traditional septic systems aren’t practical
Off-grid homes, tiny houses, cabins, and accessory dwelling units (ADUs)
Ecological demonstration projects or sustainability-focused communities

Some progressive counties (like Sonoma, Humboldt, and Mendocino) have a track record of approving certified composting toilets for permitted homes, but urban/suburban areas (like LA, Orange, or San Diego counties) may have stricter enforcement and be more reluctant unless there’s a compelling reason.

Steps for Legal Installation

Contact your local building and environmental health department:
- Ask about composting toilet rules, local amendments to the plumbing code, and the required application or permitting process.
Choose a certified composting toilet system:
- Look for NSF/ANSI Standard 41 certified models. Save documentation for permitting and inspection.
Submit a site and plumbing plan:
- Include details about the composting toilet and your proposed greywater system or septic solution. Some counties may require a soil analysis or perc test.
Get permits and schedule inspections:
- Install according to manufacturer and code requirements. The inspector may require proof that you’re managing all waste safely and legally.
Maintain your system:
- Keep maintenance logs, receipts, and follow all manufacturer instructions. Improperly maintained toilets can be ordered removed.

What About Off-Grid or DIY Projects?

For truly remote cabins or unpermitted structures, enforcement is more relaxed, but the risk is yours. If you want to get a certificate of occupancy, insurance, or eventually sell, legal compliance is strongly recommended. Many counties have cracked down on “bucket toilets” and unsanitary practices after complaints or code enforcement sweeps.

Penalties and Risks

Installing a composting toilet without permits, using an unapproved system, or mishandling waste can result in fines, stop-work orders, forced removal, or delays in building approvals or property sales. If a neighbor or visitor complains about odor, pests, or groundwater pollution, code enforcement may inspect—even years after installation.

Greywater and Liquid Waste Rules

Composting toilets deal only with solid human waste and (depending on design) urine. All household greywater must be handled separately, either by:

An approved greywater irrigation or dispersal system (per Title 24 rules)
A traditional septic tank and leach field (most common in rural areas)
Connection to a municipal sewer system (in cities/towns)

Direct surface discharge of greywater (even from a tiny house or cabin) is almost always illegal unless specifically permitted.

Tips for Success

Start by calling your county environmental health department—they set the tone for what’s allowed.
Stick with certified, manufactured composting toilets for easiest approval.
Prepare a thorough waste management plan, addressing both solids and greywater.
Keep all paperwork and maintenance records for resale or inspections.
If you’re buying rural land, check zoning and water/sewer rules before you close the deal.

Helpful Resources

Final Thoughts: Composting Toilets in California—Legal, But Plan Carefully

Composting toilets are legal, sustainable, and gaining ground in California, but you must plan carefully to navigate the complex rules. Start by checking local codes, choose a certified system, and work with your county to get approval. The reward? Sustainable living, peace of mind, and a cleaner, greener Golden State.