Ferguson’s Seattle plumbing supply branch on 6th Avenue S sells plumbing products, including water heaters, pumps, pipe, valves, fittings, equipment, faucets, fixtures and accessories. It also sells HVAC supplies. The branch page is aimed mainly at contractors and does not say whether it serves walk-in homeowners, so call first.
Posted hours are Monday to Friday, 5 am to 3 pm, closed weekends.