#1 · SEATTLE
Commercial plumbing serves restaurants, offices, retail, and multifamily buildings — grease traps, backflow assemblies, floor drains, commercial water heaters, and code-driven work that residential plumbers don't touch daily.
Wet-side market range — get itemized quotes before work starts
Companies whose focus matches this work are listed first, then Seattle's other top-rated plumbers. Same no-pay-to-play ranking as everywhere on Wetside Plumbing — the formula.
Google Business data, 2026-08-07. See the full Seattle ranking →
Also searched as: commercial plumber, commercial plumbing commercial plumbing, commercial plumbing company, commercial plumbing repair, hoa plumbing, mobile home plumbing.
You want one who does grease interceptors and health-code work weekly, not occasionally. Ask specifically about interceptor sizing and pumping schedules — the answer tells you their experience level fast.
Water districts require annual testing of backflow prevention assemblies to keep contamination out of the public supply. Only certified testers can file the paperwork; many commercial plumbers carry the certification.
Ask for their Washington L&I contractor number and verify it at secure.lni.wa.gov/verify — active license, bond, and insurance. Listings above with a green badge are ones we've already matched to an active license in state records.