The short answer
- Who is responsible
- The property owner is responsible for the entire private sewer lateral, from the building to the public sewer main, including the wye connection to the main.
- What triggers an inspection
- Selling a home, Remodel or addition, Sewer overflow, Change of use.
- Who does it
- A licensed plumber or contractor must perform the inspection and complete the City inspection form. The City does not perform inspections.
- What counts as proof
- The City does not issue Certificates of Compliance. The sewer lateral inspection report serves as proof of compliance.
When an inspection is required
The ordinance lists four events. The first two cover most homeowners; the other two apply to commercial and multifamily buildings.
Selling a home
An inspection is required when a detached single-family or two-family home served by a private lateral is sold, and it must be done before the sale.
Applies to detached one- and two-family homes.
Remodel or addition
An inspection is required before a building permit is issued for an addition, alteration or remodel of a detached single-family or two-family home when the project cost is over the City Council threshold, currently $90,000.
Applies to detached one- and two-family homes.
Sewer overflow
For commercial and multifamily buildings, a lateral backup or blockage that causes a sanitary sewer overflow can require an inspection. Public Works evaluates the overflow and decides.
Applies to multifamily buildings, commercial buildings.
Change of use
A change in sewer customer class can require an inspection. Per the regulations, this applies to existing commercial buildings whose new use increases wastewater strength; the City sends the owner a notice. Newly constructed buildings are exempt.
Applies to commercial buildings.
Exemptions
No inspection is needed if one of these applies.
Inspected in the last 5 years
No new inspection is needed if the lateral was inspected in the previous 5 years and that inspection found either no repairs needed, or only partial repairs that were then completed.
Fully replaced in the last 25 years
No inspection is needed if the entire lateral was replaced within the past 25 years, shown by a City plumbing permit.
Other approved exemption
The Director of Public Works can approve other exemptions.
The City lists building permits for emergency repairs or restoration as exempt from the inspection requirement. That exemption appears on the City's web page but not in the ordinance text, so confirm it with Public Works before relying on it.
Who owns the lateral
The property owner is responsible for the entire private sewer lateral, from the building to the public sewer main, including the wye connection to the main. The City does not repair, replace or clean private sewer laterals.
- Lateral starts at the building
- Cleanout
- Property line
- Under the sidewalk and street
- Wye connection
- Public sewer main
- This responsibility applies even where the lateral runs under the street (public right-of-way) or through a private easement. Private Sewer Lateral Cost Sharing Program FAQ(source: Private Sewer Lateral Cost Sharing Program FAQ, opens in a new tab)
- When a lateral is installed or replaced and there is no cleanout, the owner must add one near the building. SMMC 7.38.432(b)(source: San Mateo Municipal Code §7.38.432, Private sewer laterals, opens in a new tab)
Proof and City records
- The City does not issue Certificates of Compliance. The sewer lateral inspection report serves as proof of compliance.
- The City keeps inspection results and completed repairs in its permitting system. Questions about an existing inspection go to the Public Works encroachment permit team.
- To ask whether an earlier inspection is on file for a property, contact the Public Works encroachment permit team at pwencroachment@cityofsanmateo.org.
For a past full replacement, the evidence is the City plumbing permit. The City's permit lookup shows permits by address.
Not sure which rule applies to you?
The checker asks about your property and what's happening, and points to the rule that likely applies.
After the inspection
To pass, the lateral needs a standard building cleanout (no P-trap), no outside drains or sump pumps connected, no grade 5 structural defect, no grade 4 or 5 operational defect, a total defect score under 13, and full pipe visibility on video.
A pass means the completed form goes to Public Works and no repair work is required. A fail lists the required work, and the deadline depends on why the inspection was done.
Questions
Who owns the sewer lateral in San Mateo?
The property owner is responsible for the entire private sewer lateral, from the building to the public sewer main, including the wye connection to the main.
This responsibility applies even where the lateral runs under the street (public right-of-way) or through a private easement.
Does the City ever pay to fix a private lateral?
Not directly. The City runs a reimbursement program for full replacements.
The City does not repair, replace or clean private sewer laterals.
For FY 2026/27 the City reimburses 50% of the lowest approved bid for a full lateral replacement, up to $2,500, while funding lasts.
What remodel value triggers an inspection?
The remodel trigger threshold set by City Council is $90,000.
An inspection is required before a building permit is issued for an addition, alteration or remodel of a detached single-family or two-family home when the project cost is over the City Council threshold, currently $90,000.
Does a condo or townhome need an inspection?
The City's regulations apply the sale and remodel requirements to detached single-family and two-family homes. If you own a condo, townhome or a building with three or more units, confirm with Public Works whether a requirement applies to you.
How do I find out whether an inspection is already on file?
To ask whether an earlier inspection is on file for a property, contact the Public Works encroachment permit team at pwencroachment@cityofsanmateo.org.
The City keeps inspection results and completed repairs in its permitting system. Questions about an existing inspection go to the Public Works encroachment permit team.