Find out whether a Peninsula neighborhood is on septic or city sewer — and what it means for your purchase, renovation, or sale.
Primarily four pockets: Woodside (almost entirely septic), Portola Valley (mostly septic outside Ladera), Los Altos Hills (mostly septic), and the western edges of Atherton and West Menlo Park near the foothills. Emerald Hills (the unincorporated hillside above Redwood City) is also significantly septic. Within nominally sewered cities, isolated septic parcels can remain on hillside lots that pre-date connection ordinances.
Three implications. First, the system needs inspection during contingency — a Septic Inspection by a licensed contractor typically runs $500-$1,200 and pulls the leach field history. Second, system replacement costs $25K-$80K depending on capacity and soil. Third, a failing septic field can constrain ADU and remodel feasibility — many Peninsula towns require septic capacity verification before expanding bedroom count. Always get a recent (within 6 months) septic inspection report.
The sewer lateral is the underground pipe connecting your home to the city's sewer main, typically running under the front lawn and out to the street. Most Peninsula cities require a Lateral Inspection at the time of sale (or at a triggering event like a remodel). If the lateral has root intrusion, cracks, or collapse, the seller (or buyer, depending on local custom) is responsible for repair before closing. Lateral replacement costs $8K-$25K depending on length and access. Burlingame, San Mateo, and several other cities have specific time-of-sale lateral inspection ordinances.
Sometimes yes, sometimes no. The constraint is whether a city sewer main runs in your street. In Woodside, Portola Valley, and Los Altos Hills, the answer is usually no — the city has chosen not to run sewer mains, so septic is the only legal option. In edge-of-city pockets within otherwise-sewered cities, retroactive connection is sometimes possible but expensive ($50K-$150K including main extension). For most buyers, plan to live with what the property has rather than convert.
Send Lisa the address and she'll pull the title prelim and confirm sewer status, lateral inspection requirements, and any open code violations.
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