Serving San Francisco
Groundwater & Basement Water Intrusion in San Francisco, CA
Basement seepage, failed sumps, and hydrostatic pressure against the foundation are extracted and dried, and the path from the ground is identified so the loss does not repeat. Groundwater and basement seepage are extracted and dried only after the path from the soil is identified — a wall, a slab, a drain, or a failed sump. Drying the interior without stopping that path returns the same water to the same floor.
Frequently asked questions
Water gathers in the same block every time and nowhere else.
Those are usually the old creek lines and the hollows they ran through, buried but not removed. Water still finds the low route it always took, and where the street was laid across a filled hollow it collects there. City mapping of the historic watercourses explains a great many of these spots, and it is worth looking at rather than guessing.
It welled up out of the basement floor while the street stayed dry.
The main running full relieves itself through the lowest connected opening it can find, and in a house like this that is the basement drain. What arrives is the street's water rather than anything from the ground. Nothing done outside the building touches it; a valve on the line or lifting the drainage above street level with a pump does.
The hill street outside runs like a creek and the drains catch nothing.
On grades this severe the flow is moving fast enough to skip a grate entirely, and the lowest block of a hill collects what every block above it shed. That is a limit of the arrangement rather than a blockage. The useful work sits at the property line, turning the flow aside before it reaches an entrance.
This FAQ belongs to the San Francisco page; it is repeated here.