What is a sewer lateral inspection and is it required?

A sewer lateral inspection sends a video camera down the sewer pipe to assess its condition from the inside — revealing root intrusion, cracks, offset joints, bellies, and blockages that are completely invisible from the surface. It is not always required by code, but on an ADU project it is one of the smartest few hundred dollars you can spend.

What the camera reveals

• Root intrusion at pipe joints — the leading cause of failure in older clay laterals.
• Cracks, fractures, and crushed sections from soil movement or tree pressure.
• Offset or separated joints where pipe segments have shifted.
• Bellies (low spots) that pool waste and cause chronic backups.
• Material and diameter — confirming whether you have clay, cast iron, Orangeburg, or modern PVC, and whether the line is large enough for the added ADU load.

Why it matters before you build an ADU

The economics are the whole argument. If your lateral is deteriorated, replacing it during the ADU project — while trenches are open and landscaping is already disturbed — is dramatically cheaper than excavating again after the unit is finished, the patio is poured, and the yard is replanted. The inspection also confirms the lateral has the capacity to carry the new fixture-unit load, and it gives you documentation to budget repairs with confidence instead of discovering a failed line mid-construction.

Is it required?

It depends on where you are. A number of California cities — particularly in older neighborhoods with aging clay infrastructure, and many East Bay and coastal jurisdictions — require a point-of-sale or point-of-improvement lateral inspection (and sometimes a compliance certificate) as a condition of permitting. Even where it is not mandated, most experienced ADU builders treat it as standard due diligence.

Lateral inspection and compliance-certificate requirements vary by city and sewer district. Confirm with your local building department or sewer authority before you finalize plumbing design.

Cost and timing

A camera inspection typically costs $150–$350 and takes about an hour. If the line is healthy, you get peace of mind and a clean tie-in. If it is failing, you have found the problem at the least expensive possible moment to fix it. Either way, schedule it during early planning — before architecture and site design are finalized — so the results can shape the plumbing design rather than blow up the budget later.