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Marin County Septic Systems: Inspections, Classes and the LAMP Update

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Marin County does not require a septic inspection when a home sells, but the seller must disclose the system’s condition, and many buyers ask for the septic records and an evaluation. Septic systems are permitted by Marin County Environmental Health Services (EHS), which grades every system from Class I to Class IV and puts alternative systems on an annual operating permit. In Stinson Beach the water district runs its own onsite program, and its discharge permits are reissued when a parcel changes hands.

The county says most of West Marin and pockets of east Marin use individual septic systems, and that if you don’t pay a sewer bill, you are probably on one. The rules themselves are being rewritten: the county’s new Local Agency Management Program, or LAMP, was targeted for the end of 2026, but the draft has slipped.

This guide explains how the current system works, what to pull before you list or make an offer, and where the update stands. For the wider market, see our Marin County real estate guide.

Who regulates septic systems in Marin

For most properties outside the sewer districts, the regulator is EHS, part of the county’s Community Development Agency. It issues permits for new systems and repairs, keeps the records, and reviews building permits that affect a septic system. Its septic team is at 3501 Civic Center Drive, Suite 236, San Rafael, and on 415-473-6907.

The county works within a statewide framework. The State Water Resources Control Board first adopted its onsite wastewater treatment system (OWTS) policy in June 2012 and renewed it in April 2018 and again on April 18, 2023. Marin’s LAMP page describes the county as a Tier 2 local agency still operating under regulations and county code last amended in 2011.

Two communities have their own arrangements:

Stinson Beach. The Stinson Beach County Water District manages onsite wastewater under Title IV of its code, with its own design review, permits and inspections. See our Stinson Beach guide.
Bolinas. The Bolinas Community Public Utility District sewer serves 141 residential, 20 commercial and 2 institutional properties, mainly in the downtown village, and has had a moratorium on new connections since 1985. Homes outside it use onsite systems under county rules. Our Bolinas guide covers the water moratorium as well.

What the septic classes mean

Every system in the county’s records carries a class. It is the quickest way to judge how a system compares with current standards, and buyers ask for it first.

Class	County description	What it usually means for a sale
Class I	Code complying: a dual leach field (200% sizing) that meets all siting and design criteria	The strongest file; a replacement field is already designed in
Class II	Repair standards: a 100% sized field that meets much of the siting and design criteria	Workable, but there is no spare field if the current one fails
Class III	Existing: permitted under current or previous rules, but below Class II standards	Expect questions on age, capacity and what a repair would involve
Class IV	Undocumented or unapproved: redwood, steel or cinder-block tanks, a cesspool, no permit record, or a failed system	Buyers and lenders will want an evaluation; some systems can be permitted retroactively

The class reflects the county’s file, not the system’s current performance. A Class III system can work well, and a Class I system can be poorly maintained. That is why an evaluation matters even when the paperwork looks good.

Operating permits for alternative systems

Where a standard tank and leach field won’t work, Marin allows several kinds of alternative systems, which are designed for the specific site. The county says alternative systems need an annual operating permit and professional monitoring, and that the owner holds the operating permit for the life of the system.

Qualified professionals and licensed septic contractors do the inspections and submit the monitoring reports. For a buyer, that means a recurring cost and a paper trail. For a seller, it means the current permit and recent monitoring reports belong in the disclosure package, because their absence is the first thing a buyer’s inspector will note.

Septic at sale: what the county requires and what buyers expect

Marin has no point-of-sale septic inspection. The county’s LAMP page says sellers must disclose the system’s condition, and it describes no new sale requirement in the update. EHS staff will answer questions about a system during a sale, and the department publishes a residential inspection form for performance evaluations done for remodels or real estate sales.

In practice, many buyers make an evaluation a contingency. An evaluation done before listing, on the county’s form, lets a seller price the house with the answer in hand and avoids a surprise renegotiation in escrow. Our guide to well and septic inspections in Napa and Marin explains what an inspector looks at.

Stinson Beach: permits follow the parcel

Stinson Beach adds a step. Under the water district’s code, a discharge permit is issued to a specific property and recorded with the County Recorder, and “Discharge Permits shall be reissued in cases of parcel ownership change” (Section 4.06.610). The district’s fee schedule lists a $45 change of ownership administrative fee and $200 for reissuing a recorded discharge permit.

The code also makes every system subject to regular inspection as district staff decide, and a revoked permit is reissued only after the district verifies corrective work. Ask the district at (415) 868-1333 about the parcel’s permit status before you set a closing date.

A records checklist before you list or make an offer

Search the county archive. EHS keeps an online archive of digital septic records. Search it by parcel number and save the permits, the class and any repair history.
Match bedrooms to the design. Current rules design systems at 150 gallons per day per bedroom, with a 30% reduction allowed for water-saving fixtures, so most modern systems are designed at 105 gallons per day per bedroom. If the listing shows more bedrooms than the permit, expect the buyer to ask about the gap.
Collect maintenance records. Pumping receipts, repair invoices and, for alternative systems, the operating permit and monitoring reports.
Order an evaluation. Use a qualified septic inspector and the county’s residential inspection form. Sellers often do this before listing; buyers do it during the contingency period.
Check the location. The county says additional permits may be needed in the Coastal Zone or a Stream Conservation Area, which matters for any repair or addition.
Check district charges. In Stinson Beach and the Bolinas sewer area, gather recent bills or tax-bill charges so the buyer can see the ongoing cost.

Septic is one item on a longer list. Our Marin selling requirements by town covers sewer laterals, resale reports and fire inspections, and the state disclosure forms are explained in our California seller disclosures guide.

Repairs, remodels and ADUs

A county permit is needed to replace or repair a septic tank, excavate or alter the disposal field, replace sand media or gravel, replace a pretreatment unit or other component, or abandon a tank or system. Some work is exempt, including pump and control panel work (which may need an electrical permit), routine field maintenance, and installing or repairing risers and effluent filters.

If a system is failing, the county says the tank can be capped to stop surfacing sewage and used as a holding tank until the repair, and an approved designer should start the permit process. A buyer who finds a failing system in escrow should price the design, permit and construction time, not just the contractor’s bid.

Remodels and additions follow the county’s Residential Improvement Policy, and building permit applications involving a septic system are routed to EHS for review. The LAMP page notes that ADU planning and home improvements can trigger septic review. On a small lot, the septic system often decides whether a second unit or an extra bedroom is possible, so check before you design, and see our Marin land guide if you are buying a lot.

The LAMP update: where it stands in October 2026

Marin has been updating its septic rules since 2014. The county hired consultants with the goal of an adopted LAMP by the end of 2026, and in September it expected a public draft in mid-October and a first reading at the Board of Supervisors on November 10.

That schedule has moved. As of the county’s October 16, 2026 update, staff had determined that resolving the remaining complex issues would take more time, no draft had been released and no new release date was given. The November 10 meeting is now an informational progress update from the Community Development Agency, with the staff report and presentation to be posted on November 5.

The update needs approval from the Regional Water Quality Control Board, acting for the State Water Board, and from the Board of Supervisors. Based on the county’s descriptions, it may:

lower design flows below the current 150 gallons per day per bedroom;
allow more kinds of alternative systems;
revise septic installation, inspection and permitting procedures.

The county says a Marin-specific LAMP would allow more flexible wastewater calculations, which could ease limits on home improvements and housing. Until it is adopted, the 2011 rules apply.

More than 500 people took part in nearly 60 community and individual meetings, including sessions in Point Reyes Station, Bolinas, Dillon Beach, Muir Beach and the San Geronimo Valley. We will update this page after the November 10 meeting.

Town by town

Each West Marin community has its own mix of sewer, shared and individual systems. Our town guides cover the local details for Point Reyes Station, Inverness, Olema, Marshall, Tomales and Muir Beach, along with the Stinson Beach and Bolinas pages above.

This is general information, not legal or engineering advice; talk to a licensed septic designer or engineer and a California real estate attorney about a specific property.

Questions people ask

Does Marin County require a septic inspection when you sell a house?

No. The county has no point-of-sale septic inspection, and its LAMP update describes none. Sellers must disclose the system’s condition, and Environmental Health publishes an inspection form for real estate sales.

How do I find the septic records for a Marin property?

Search Environmental Health Services’ online archive of digital septic records by parcel number, or call the septic team at 415-473-6907. Save the permits, the system’s class and any repair history.

What is a Class IV septic system in Marin?

It is the county’s class for undocumented or unapproved systems: tanks of redwood, steel or cinder block, cesspools, systems with no permit record, and failed systems. Some can be permitted retroactively.

Do alternative septic systems need a permit every year?

Yes. The county says alternative systems need an annual operating permit and professional monitoring, and the owner holds the permit for the life of the system.

What happens to a Stinson Beach septic permit when the house sells?

The Stinson Beach County Water District reissues the recorded discharge permit on a change of ownership. Its fee schedule lists a $45 change of ownership fee and $200 for reissuing the permit.

When will Marin’s new septic rules take effect?

No firm date is set. The county still describes the end of 2026 as its target, but as of October 16, 2026 the public draft had been delayed with no new release date, and the November 10 Board of Supervisors item is an informational update. It also needs Regional Water Board approval.

Can I add a bedroom or ADU to a house on septic in Marin?

Possibly, but septic capacity often decides it. Building permits that involve a septic system go to Environmental Health for review, and current rules size systems by bedroom count. Have a septic designer check the site first.

If you are buying or selling a West Marin home, we can help you pull the county septic file and permits early and price the property with them in hand; see how we approach a Marin County home sale or contact us about a specific parcel. Diamond may refer you to partners we work with, such as septic inspectors; you’re free to choose any provider.

Sources & notes

Last reviewed October 2026 by Matthew Martinez.