A seller in Burlingame gets a witnessed test, a plumber standing next to a city inspector while water fills the line. A seller in Hillsborough gets a camera run through the pipe and a compliance certificate to hand a buyer at closing. A seller in San Mateo gets neither. The city requires the same underlying inspection, at the same moment in the transaction, and then hands the seller a piece of paper the city itself calls an inspection report, not a certificate, because San Mateo does not issue one.
That difference sounds like a technicality until you are the one trying to prove, three weeks before closing, that your home already complies.
The ordinance reads like everyone else's, until you get to what it skips
San Mateo's Private Sewer Lateral Ordinance, part of Municipal Code Section 7.38.432, took effect December 1, 2020, after the city council amended it that February to cut down on sanitary sewer overflows. It applies to detached one- and two-family homes served by a private sewer lateral, and it triggers an inspection under four circumstances: sale of the property, a building permit for an addition or remodel valued at $90,000 or more, a sewer backup that causes an overflow at a commercial or multifamily building, or a change in sewer customer class.
For a home sale, that means the seller is on the hook for hiring a licensed plumber to inspect the lateral, whatever method the plumber chooses. The city does not send anyone to watch. There is no city representative on site, no video review board, no compliance stamp issued afterward. The plumber files the results, and that filing is the entire record.
Compare that to Burlingame, where Ordinance 1329 requires a witnessed infiltration test for any building 25 years or older before it can sell, with a city representative present to watch the test happen. A video recording does not satisfy the requirement there. Hillsborough has run its own version since 2012, where the seller either cameras the lateral or tests it at the main and receives a formal compliance certificate before escrow closes. San Bruno's rule, effective May 8, 2015 under Municipal Code 10.13, applies to homes 50 years or older and also ends in a Sewer Lateral Compliance Certificate. Millbrae's ordinance, Municipal Code 8.20.450, requires a full in-line video inspection from the building to the main, plus its own compliance certificate.
San Mateo sits in the same regional family of point-of-sale sewer lateral rules as these four cities, plus Pacifica and South San Francisco. It just built the loosest version of it.
What "passing" actually measures
The inspection itself is a grading exercise, not a binary pass or fail. Under the city's administrative regulations, a lateral passes if it has no pipe with a structural grade of 5, no operational defect graded 4 or 5, and the sum of every defect grade found in the line comes in under 13. That means a lateral with several smaller defects can still fail on the cumulative score even if nothing individually looks catastrophic. It also means two plumbers using different judgment calls on borderline defects could reasonably produce different totals on the same pipe.
That is the tradeoff behind letting the seller's own contractor choose the method and score the result. It is faster and cheaper than a witnessed test, but it puts more weight on the seller having hired a plumber who documents thoroughly, because there is no independent third party checking the math afterward.
How San Mateo compares to its neighbors
| City | Inspection method | Age or value trigger | Ends in a certificate? |
|---|---|---|---|
| San Mateo | Contractor's choice of method, unwitnessed | Sale, or remodel ≥ $90,000 | No, inspection report is the proof of compliance |
| Burlingame | Witnessed infiltration test (Ordinance 1329) | Buildings 25+ years old, at sale | Not applicable, a pass is valid 10 years or 25 after full replacement |
| Hillsborough | Camera or main-line test, city program since 2012 | At sale | Yes, formal compliance certificate before escrow closes |
| San Bruno | Inspection under Municipal Code 10.13 | Homes 50+ years old, at sale | Yes, Sewer Lateral Compliance Certificate before title transfers |
| Millbrae | In-line CCTV video, full length to the main | At sale (Municipal Code 8.20.450) | Yes, compliance certificate before ownership changes |
Read across that table and the pattern is obvious. Every neighboring city either raises the bar on how the test is performed or lowers the risk by issuing a document the seller can point to later. San Mateo does neither. It asks for the inspection, then leaves the seller holding a report instead of a certificate, which shifts the burden of proof onto whoever kept the paperwork.
Why the missing certificate becomes a timing problem
Two exemptions matter more in San Mateo than they do elsewhere, precisely because there is no certificate backing them up. A property is exempt from a new inspection if it can show a passing inspection within the prior five years, or if the lateral was completely replaced within the past 25 years with a plumbing permit on file. Both are reasonable rules. Both also depend entirely on the seller producing a document the city itself will not reissue.
That is where the ordinance's age works against long-time owners. It only started in December 2020. A seller who has owned since, say, 2015 and did no remodel large enough to trigger the older rules has simply never been inspected under this ordinance. There is no five-year lookback to claim, because there is nothing in the file to look back on. That seller is not exempt. They are inspecting for the first time, on a listing timeline, with no city-issued paperwork to fall back on if a question comes up about a prior test that predates the rule entirely.
The city's own cost-sharing program adds a second timing trap. San Mateo runs a Private Sewer Lateral Cost Sharing Program that helps offset replacement costs, and the city's active annual reporting through the 2025-2026 cycle confirms it is still running. But the application has to be submitted and approved before the replacement work starts. A seller who gets a failing result during escrow and rushes a contractor in to fix it before the buyer's inspection contingency expires has likely already missed the window to apply. The grant exists for people who plan ahead, not for people reacting to a surprise thirty days before closing.
A sequence that avoids the surprise
For anyone preparing to list a single-family home in San Mateo, the order of operations matters more than the individual steps:
- Search your own records for a sewer lateral inspection report dated after December 1, 2020. If one exists and it passed, you are exempt for five years from that date.
- Check your permit history for any remodel valued at $90,000 or more, or a full lateral replacement, either of which may already have satisfied the requirement or started its own exemption clock.
- If neither applies, schedule the inspection before you list, not after you accept an offer. A failing result found early leaves time to apply for the cost-share program before repair work begins.
- Keep the plumber's inspection report yourself. Because the city will not issue you anything else, that report is the only document you or a buyer's agent can point to later.
- If you are buying rather than selling, ask for the actual inspection report rather than a verbal assurance that the lateral "passed." In San Mateo specifically, there is no certificate number to verify against a city database. The report is the whole record.
That last point matters for anyone comparing a San Mateo listing against one in Burlingame or Hillsborough. A phrase like "sewer lateral compliant" carries a witnessed test and a real certificate in one city and a self-reported, unwitnessed score in another. They are not the same assurance, even though they sound identical in a listing sheet.
FAQ
Does every home in San Mateo need a sewer lateral inspection to sell? Only if none of the exemptions apply. A passing inspection within the past five years or a full lateral replacement within the past 25 years, documented by permit, both exempt the property from a new inspection at sale.
Does San Mateo give sellers a certificate to show buyers? No. The city does not issue a Certificate of Compliance for sewer laterals. The licensed plumber's inspection report is the proof of compliance, and it is the seller's responsibility to keep and share it.
What if my lateral fails the inspection? The property owner is responsible for repair or replacement. If you want to use the city's cost-sharing program to offset the expense, the application needs to be submitted and approved before the work begins, so timing the inspection early in your listing prep matters.
Is San Mateo's rule stricter or looser than Burlingame's? Looser in method. Burlingame requires a witnessed infiltration test with a city representative present. San Mateo lets the seller's own contractor choose the inspection method and self-report the result, with no city witness involved.
If you are getting ready to sell a San Mateo home, or comparing it against a listing across the city line in Burlingame or Hillsborough, this is exactly the kind of detail worth walking through before you sign a listing agreement, not after an offer arrives. Charles Griffith and the Griffith Partners team can help you check what's already on file for your property and build a pre-listing timeline that accounts for it. Reach out for a free home valuation and a straight answer on where your lateral stands.