If you’ve been in a lot of basements in San Francisco, you’ll have noticed some foundations have water stains with a chalky, white appearance. This is called “efflorescence”. This develops as the salt minerals in the concrete slough off as water drains through the concrete. And yes, concrete is porous and not watertight.
I often get asked the question, “Does this have to be repaired?” or, “Will the foundation need to be replaced?” Like most things, it depends on the frequency and length of time the issues have been going on. It can take years, if not decades for efflorescence to affect the structural integrity of the concrete. However, if not addressed, it can eventually affect the integrity of the concrete.
My recommendation is to always first address the source of the problem which is often a drainage issue, and then to figure out if or when a foundation repair is necessary. If you can’t solve the problem, it will just keep coming back.