You're standing in a gravel driveway off Hayes Valley, six acres in front of you, half planted in vines, the kind of property that shows up in a listing photo with the words "build your dream home" over a shot of rolling hills near CordeValle. Your agent mentions the septic clearance is already in place. You nod. In your head, that phrase does a lot of work: cleared, inspected, verified. Somewhere between the drive down US-101 and the offer you're about to write, you've filled in a blank the county never actually promised to fill.
That gap between what a phrase like "septic clearance" sounds like it means and what Santa Clara County actually requires is the single most consequential piece of due diligence most San Martin buyers skip, not because anyone hides it from them, but because it isn't required to exist at all.
The paperwork everyone assumes is there
Cross the county line into Santa Cruz County and the rules are explicit. Since July 1, 2023, any seller of rural real estate there must have the septic tank pumped and inspected, with a flow test and a disclosure form filed with the county's Environmental Health Division before the sale closes. Since September 1, 2025, that county has gone further, requiring the private well itself to be tested for yield and water quality at the time of transfer, with the results disclosed to both the buyer and the county.
Santa Clara County, where San Martin sits, has no equivalent ordinance. The county's own Department of Environmental Health answers the question directly on its site: a septic inspection is not required before a sale. It's recommended, so the results can be folded into the property sale disclosure, but recommended and required are different words with different consequences. There's no parallel requirement for well water testing at all. The department does suggest pumping a tank every three to five years to avoid drainfield failure, but that guidance was never written into the ordinance.
What that means in practice: the Transfer Disclosure Statement covers what the seller already knows. If nobody has tested the well or pumped the tank in years, there is nothing to disclose because there is nothing to know. The paperwork can look complete and still tell you almost nothing about the two systems that keep a rural San Martin property livable.
| Santa Cruz County | Santa Clara County | |
|---|---|---|
| Septic inspection at sale | Required since July 1, 2023 | Recommended only, not codified |
| Well water quality/yield test at sale | Required since Sept. 1, 2025 | Not required |
| Who files the report | Seller, via county's point-of-sale process | No county filing requirement |
| Failing system found before close | Seller repairs, or transfers responsibility to buyer in writing | No formal transfer-of-responsibility process |
What's actually in the ground under San Martin
The reason this gap matters more in San Martin than in, say, a subdivision with municipal water is straightforward: almost nobody here is on a public system. Valley Water, the district that manages groundwater for the county, has said that in South County the share of water supply coming from underground aquifers runs close to 100 percent. Every home on well water is drawing from the same shared resource, and that resource has a documented problem.
San Martin sits over the Llagas Subbasin, and Valley Water's Water Year 2025 Groundwater Report, published in March 2026, put a number on it: a quarter of the Llagas Subbasin wells tested had nitrate concentrations above the federal drinking water standard, almost all of them domestic wells rather than public supply wells. Sixty individual wells came back over the limit. One public supply well also showed detections of PFOA and PFOS above the maximum contaminant level. Valley Water's own report states plainly that the district has no regulatory authority over the activities that load nitrate into groundwater in the first place, meaning septic systems and agriculture, which happen to be the two land uses that define San Martin.
None of that means a given property's water is contaminated. It means a one-in-four chance, on the specific aquifer under this specific community, is not a rounding error. It's a real enough number that skipping the test because the county doesn't ask for one is a choice, not an oversight.
2026 made the well itself more expensive and more digital
If you're buying raw acreage with the intent to drill rather than acquiring a home with an existing well, two changes this year raise the cost of getting it wrong. Valley Water's well permit fees increased on January 1, 2026, the first change to that fee schedule since 2017, covering construction, destruction, reconstruction, exploratory boring, and standby permits, plus new surcharges for weekend or holiday inspections. Then, starting February 1, 2026, the district stopped accepting paper applications entirely. Every well permit now has to go through the CityWorks online portal, and the account has to be registered in the name of the individual applicant, not a business entity.
The process itself hasn't gotten faster. A new well still needs a Santa Clara County Environmental Health clearance first, which takes roughly five working days for a site visit, before the paperwork moves to Valley Water for the construction permit, which takes another one to two weeks. Only a licensed C-57 well drilling contractor can perform the actual work. If you're budgeting a build timeline around a well that doesn't exist yet, plan for that sequence, not the date you'd like to break ground.
What to do during your contingency period
None of this is a reason to avoid San Martin. It's a reason to stop treating the disclosure packet as the finish line. A few things worth doing before your contingency period expires, regardless of what the seller's TDS says:
- Order your own septic pump and inspection through a contractor on the county's approved Septic System Contractor's list, even though it isn't legally required. The Onsite Systems Manual that governs installation permits in the county references that list directly, and it's the same standard a repair permit would need to meet later.
- Pay for an independent water test covering nitrate and coliform bacteria at minimum, given what the Llagas Subbasin data shows. A well that's been fine for the current owner for twenty years can still test high for nitrate; concentrations move with rainfall, irrigation timing, and upstream land use, not just with the well itself.
- If the property needs a new or reactivated well, get the C-57 contractor's timeline in writing before you waive your contingency, and price in the current CityWorks-era fee schedule rather than whatever number the seller's agent quotes from memory.
- Ask specifically whether any existing OWTS on the property has ever required an alternative or enhanced treatment system. Santa Clara County only mandates those on sites with high groundwater, steep slopes, or other constraints a conventional system can't handle, and retrofitting one later is a materially different cost than maintaining a conventional tank and drainfield.
Why people still buy here anyway
The trade-off is real in both directions. San Martin's Rural Residential designation, set out in the county's San Martin Planning Area policies, is exactly what protects the acreage, the working vineyards, and the equestrian character that draws buyers away from subdivided South County in the first place. Clos LaChance Winery, tucked into Hayes Valley off Hummingbird Lane, still runs its tasting room and its KRTY Song and Wine concert series a few minutes from the sixth hole at CordeValle. Coyote Lake-Harvey Bear Ranch County Park, 6,695 acres of oak woodland and a 449-acre lake, keeps its boat launch open into October. San Martin Airport still offers private pilot lessons to residents who bought the acreage partly for that reason. None of it runs on a municipal hookup, and that's the point.
Buying into that lifestyle just means owning the diligence the county doesn't own for you.
Frequently asked questions
Is a septic inspection legally required before I can close on a San Martin property? No. Santa Clara County's Department of Environmental Health recommends pumping and evaluating a septic system as part of the sale disclosure, but it has not codified that recommendation into a requirement, unlike Santa Cruz County next door.
Does the seller have to test the well before selling? There's no Santa Clara County ordinance requiring a well water quality or yield test at the time of sale. Any test that happens is because the buyer or seller chose to order one.
What if my water test comes back high for nitrate after I'm already in contract? That's a negotiation point, not an automatic deal-breaker. Options typically include a filtration system, a deeper well, or renegotiating price to cover treatment costs, but you need the lab results in hand during your contingency period to have that conversation from a position of leverage rather than after you own the problem.
How long does it take to get a new well permitted in 2026? Budget for a county Environmental Health clearance first, roughly five working days for the site visit, followed by one to two weeks for Valley Water to issue the construction permit once the clearance is forwarded. All applications now go through the CityWorks online portal only.
If you're weighing a San Martin property and want a read on what a specific parcel's well, septic, and zoning history actually looks like before you write an offer, Jeet Sangha can walk through it with you. Request your free home valuation and we'll start with what the county records actually say, not what the listing implies.
