Restaurants and Wineries on Septic in California

Sourced from OWTS Policy Section 2.6 and the State Water Board’s commercial food service fact sheet — last checked August 2026.

Who This Applies To

Any commercial food service building served by an onsite wastewater treatment system. In California that’s a substantial group — rural restaurants, wineries and tasting rooms, roadhouses, resorts and lodges, and food service at agricultural operations.

The OWTS Policy primarily addresses domestic wastewater with subsurface disposal, but it explicitly covers commercial food service buildings with similar systems.

The Two Conditions

Under Section 2.6, you must apply to the Regional Water Board for WDRs if your system:

1. Receives wastewater with a biochemical oxygen demand (BOD) greater than 900 milligrams per liter, or

2. Does not have a properly sized and functioning oil/grease interceptor

The state is explicit that owners must comply with both requirements — along with flow limits — to avoid having to apply for WDRs.

Why BOD Matters

Biochemical oxygen demand measures how much oxygen bacteria need to break down organic material in wastewater. Food service wastewater carries far more organic load than residential wastewater.

A septic system sized and designed for domestic strength wastewater can be overwhelmed by high-strength commercial flow — and an overwhelmed system passes inadequately treated effluent to the soil.

Reducing BOD: What the State Actually Recommends

The State Water Board publishes practical guidance here, and it’s genuinely inexpensive to implement. Train staff to:

• Scrape plates and cookware to dispose of residual food in the trash before rinsing dishes
• Use screens in drains to capture food waste, and maintain drains and traps
• Minimize use of sink-mounted garbage disposals
• Recycle or properly dispose of cooking oils rather than pouring them down the drain
• Sweep or mop floors rather than washing spills down the drain
• Consider installing an in-kitchen passive interceptor

The state’s assessment is that employing these relatively inexpensive practices is likely to maintain BOD below the 900 mg/L threshold.

Which is worth pausing on: staff training and drain screens may be what keeps you out of a Regional Water Board permitting process. That’s an unusually high return on an unusually cheap intervention.

The Grease Interceptor

Fewer options here. The state lists three:

Connect to a regional wastewater collection system, if that’s possible.

Install a properly sized and functioning oil/grease interceptor.

Apply to the Regional Water Board for WDRs.

“Properly sized and functioning” is doing work in that sentence. An interceptor that exists but is undersized, or that hasn’t been serviced, doesn’t satisfy the requirement.

The Flow Threshold

Separate from BOD, owners of systems with projected flow over 10,000 gallons per day, or that receive high-strength wastewater, must notify the Regional Water Board. Those systems may need to submit a Report of Waste Discharge for WDR coverage, or a Waiver of WDR.

For a busy restaurant or a winery with tasting room and production wastewater, that threshold is reachable.

Wineries Specifically

Worth noting that winery process wastewater and tasting room domestic wastewater are different things, and conflating them causes problems.

Tasting room restrooms and food service generate wastewater the OWTS Policy addresses. Crush and production wastewater is a different regulatory question, generally handled through the Regional Water Board directly, and it can be high-strength and highly seasonal in a way septic systems handle poorly.

If you’re operating both on one property, it’s worth being clear with your Regional Water Board about which flows go where.

Where to Get Independent Help

For wineries specifically, UC Cooperative Extension maintains viticulture and enology advisors in most California wine regions, and winery wastewater is within their remit. A county extension office is a free, independent starting point before you commission consulting work.

What To Do

Find out your BOD. If you’ve never had wastewater tested, you don’t know which side of 900 mg/L you’re on.

Check the interceptor — is it correctly sized for your operation, and is it being serviced?

Implement the source control practices. They’re cheap and the state considers them likely to be sufficient.

Talk to your Regional Water Board before a problem forces the conversation. See our guide to the nine regions.