Main Sewer Line Cleaning in San Francisco, CA

San Francisco is unusual among large Western cities in running a combined sewer system, where stormwater and wastewater share the same pipes across the whole city. That has a direct consequence for homeowners that catches people out: during heavy rain the municipal system can surcharge, and when it does, a perfectly sound private lateral can back up because the main it discharges into is already full. If your line backs up only during storms and the camera shows a clear pipe, you do not have a sewer defect. You have a surcharge problem, and the answer is a backwater valve rather than a repair.

The water supply here works the opposite way from Southern California. San Francisco is served largely by the Hetch Hetchy system, soft granite runoff from the Sierra, so cast iron laterals do not build the heavy mineral crust that the same pipe accumulates on imported Colorado River water inland. Instead they corrode and lose wall section. That distinction matters practically: descaling is the right answer for a narrowed bore and the wrong answer for a thinned wall, and in this city the thinned wall is more common.

Ground conditions vary enormously across a small area. The Marina, South of Market, Mission Bay and the eastern waterfront sit on placed fill and soft bay mud, which keeps consolidating and is also where liquefaction concentrated during the 1989 Loma Prieta earthquake. On that ground bellies and offsets dominate. The hills are a different matter, with bedrock, steep grades and deep laterals.

The housing is largely post-1906 reconstruction, so a great deal of the city's residential pipe went in between 1906 and the 1930s, which is now a century of service on dense lots with heavy hardscape where lining frequently makes more sense than excavation.