Direct Answer
To hire a reliable plumbing contractor in San Francisco: (1) Get 3 written quotes with line-item breakdowns, (2) Verify CA license at California Contractors State License Board (cslb.ca.gov), (3) Confirm active general liability and workers' comp insurance, (4) Check Google and BBB reviews specific to San Francisco projects, (5) Never pay more than 10-30% upfront — never pay in full before completion.
Full Explanation
Red flags specific to San Francisco contractors: no physical San Francisco-area address, pressure to start immediately, cash-only payment demands, and license numbers that don't verify at California Contractors State License Board (cslb.ca.gov). Seasonal demand during summer brings out less reputable contractors.
Local Factors in San Francisco
📍Verify license: California Contractors State License Board (cslb.ca.gov)
📍File complaints: California Contractors State License Board (cslb.ca.gov)
📍Homeowner protections under CA consumer protection law
📍BBB Greater San Francisco chapter for complaints history