The club is open 24/7, and it's part of the chain of bathhouses that includes Steamworks Chicago, Steamworks Seattle, Steamworks Vancouver, and Steamworks Toronto. Clientele here is heavily from San Francisco, as well as Berkeley and neighboring Oakland, and you're apt to see guys of all ages and races, from the buff and bronzed to bears to twinks. Friday and Saturday nights are popular (drawing more tourists), and Sundays (especially the afternoons) have a huge following.
Part of what accounts for the popularity of Steamworks as well as Watergarden in San Jose is that San Francisco has no gay bathhouses, although it does have a few long-running gay sex clubs. A 1984 San Francisco court order ruled that sex venues could not rent private rooms and had to monitor sexual activity, which effectively eliminated bathhouses. Steamworks is a 20- to 30-minute drive south of San Francisco, and Watergarden is an hour south - they've continued to thrive, drawing many San Franciscans.
San Jose's Watergarden bathhouse (1010 The Alameda, 408-275-1215) is also very well-liked - fans praise the beautiful outdoor garden patio, solicitous staff, and attractive layout. It's a bit more inviting and cheery than the more industrial-looking Steamworks, but each place has its adherents, and Steamworks is more convenient to San Francisco.
San Francisco does have its gay sex clubs, the most popular being Eros (2051 Market St., 415-255-4921) in the Castro and Blow Buddies (933 Harrison St., 415-777-4323) in SoMa. Blow Buddies is most popular with the leather, uniform, fetish crowd, while Eros is relatively mainstream and has many elements of traditional bathhouses, including a sauna, steamroom, maze, as well as full and very reasonably priced (non-sexual) massage services. It's open until midnight most nights, and until 3 am Friday and Saturday nights.
All of the bathhouses and sex clubs in the Bay Area are 18-and-over, and all work hard to promote safer-sex practices.