Most Marin sellers walk into escrow braced for the buyer's home inspection. The inspection that actually holds up transactions is the one nobody schedules until the disclosure package is already out: the sewer lateral compliance certificate required by whichever sanitary district happens to sit under the property. There are roughly two dozen of these districts in the county, and they do not agree on when the certificate is due, what triggers it, or how long you have to fix a failure.
Here is the thesis, stated plainly. In Marin, the compliance rule that governs your sale is set by your sanitary district, not by the city or the county, and the smartest move for a seller is to treat the district's grace period as a negotiation lever rather than a safety net. The lateral is the pipe running from the house to the public main, and it is entirely the owner's responsibility to prove it is intact before the deed transfers.
Why Marin's Sewer Rules Are Not One Rule
The reason this catches people is that Marin has never had a countywide lateral ordinance. A 2014 Marin County Civil Grand Jury report called on the county's sewer agencies to require lateral repair when properties change hands, and each district responded on its own timeline with its own thresholds. The result is a compliance patchwork that maps to sanitary boundaries, not to city lines or ZIP codes. Two neighbors on the same street can sit in different districts and face different rules.
The practical shorthand for Marin sellers looks like this:
| District | Coverage | Point-of-sale trigger | Remodel trigger |
|---|---|---|---|
| City of Mill Valley + SASM members (Alto, Almonte, Homestead Valley, Richardson Bay) | Mill Valley and surrounding southern Marin | Yes, since June 2, 2015 | Plumbing permit or major work |
| Ross Valley Sanitary District | Larkspur, Ross, San Anselmo, Fairfax, unincorporated Kentfield, Greenbrae, Sleepy Hollow | Yes, at listing | Remodels of $75,000 or more, and bathroom additions |
| Sanitary District No. 5 of Marin County | Tiburon peninsula area | Yes, under Ordinance 2014-02a | More than $50,000 of work within a 3-year period |
| Sausalito-Marin City Sanitary District | Marin City and unincorporated areas in the district; City of Sausalito handled by its Public Works Sewer Division | Yes, when title transfers | Change of use and remodeling |
| Tamalpais Community Services District | Tam Valley | Permit required for all lateral work in the public right-of-way | Applies to construction and repair |
Sources for these thresholds are the districts' own pages:
