Brooklyn Plumbing Contractors

Built from DOB's own licence classification, not from company names: every permit in DOB Permit Issuance records the licence type it was pulled under, and this list counts permits issued under Master Plumber (MP). That makes membership here the city's determination rather than an inference from what a firm calls itself — a company appears because DOB licensed it for this work and it pulled permits under that licence. The difference is not cosmetic. Of the 60 busiest licensed master plumbers in the city, sixteen are invisible to a business-name keyword search: the trade abbreviates itself as "P&H", "PLG" and "CONTR" in ways DOB never normalised, and several of the largest — P.S.I. Mechanical, the sixth-busiest licensed plumbing permittee at roughly 2,700 permits — don't have the trade in their name at all. The remaining limit is real: a firm doing this work under someone else's licence, or under a general contractor licence, is not counted here.