The pier at the beach just off Playland, I think, was owned by the Olympic Club which piped water to Lurline Baths at Larkin and Bush, the Press Club at 555 Post, and to it's own pool. I was not aware of the Fairmont's pool using sea water.
I'm not sure of all this but think it's correct.
The Trader Joe's at Masonic and Geary seems to be built in an old reservoir. If you look at the retaining wall on the north side of the lot it slopes like a the side of a reservoir and has square holes, perhaps for uprights to support a roof.