Workers' Comp Rates for Plumbing NOC (Class Code 5183)

What's Included Under Class Code 5183

Bureau scope language places ordinary plumbing contractors in 5183 when the work is not otherwise classified. Included operations are broad: installation, service, and repair of water-supply and drainage piping, fixtures, and appliances inside and around buildings; water heater installation; backflow and fixture work; and the shop fabrication connected with the plumbing operation. The installation of underground lawn-sprinkler (irrigation) systems is included in 5183, and trenching performed by the same plumbing contractor for its own lines is included rather than split to a separate excavation code. Likewise, pipe welding and cutting done by the plumbing crew as part of its own piping work stays inside 5183 rather than splitting to welding or cutting NOC 3365 — 3365 is the residual code for a standalone contract welding business, not the incidental pipe joining on a plumbing job.

Drivers connected with the plumbing operation are included when the state phraseology lists drivers — a crew member hauling pipe, fixtures, water heaters, and tools to the job site is normally part of the 5183 exposure. A separate trucking or delivery business should not be folded into 5183 simply because the cargo is plumbing material. Like other construction codes, 5183 is duties-driven: employees are assigned by the plumbing operations actually performed during the policy year, and a clerical office employee 8810 qualifies for the standard exception only when working in a separate office away from the shop and job sites.

HVAC Reassignment and Where 5183 Ends

The most important recent boundary is HVAC. As a result of NCCI Item B-1391, heating, ventilation, air-conditioning, and refrigeration work was pulled out of several construction codes — including 5183 Plumbing, 5190 Electric Wiring, 5538 Sheet Metal, and the heating/AC duct codes — and reassigned to the newly established Code 5537 (Heating, Ventilation, Air-Conditioning, and Refrigeration Systems — Installation, Service and Repair & Drivers) in most states. A contractor that installs and services HVAC systems should verify whether its state has adopted 5537; in adopting states, HVAC payroll that once sat in 5183 now rates to 5537, and continuing to report it under 5183 is a common audit error.

Other plumbing-adjacent work also leaves 5183. Automatic fire-sprinkler installation is a separate fire-protection classification, not 5183 plumbing. Sewer-main and water-main construction in the street, gas-main work outside the building line, and large boiler installation can carry their own construction codes rather than the general plumbing NOC. Substantial excavation that goes beyond trenching for the contractor's own lines may be reviewed separately.

Independent-bureau states matter for 5183. California (WCIRB) is fully independent of NCCI, uses its own plumbing classifications and dual-wage construction rules, and may file the work under a different number; Pennsylvania (PCRB), Delaware (DCRB), New Jersey (NJCRIB), Michigan (CAOM), and North Carolina (NCRB) operate their own rating bureaus and may use different plumbing phraseology or boundary tests. A contractor in those states should check the local bureau's classification rather than rely on a national 5183 comparison.

Audit Records for Plumbing Contractors

The cleanest 5183 audit file separates payroll by job type before the policy year closes. Keep job tickets and contracts, payroll splits that distinguish ordinary plumbing from any HVAC, fire-sprinkler, sewer-main, gas-main, or boiler work, certificates for any subcontracted trades, and records showing trenching done for the contractor's own lines versus separate excavation. Reconstructing those splits after an auditor asks is far harder than assigning crews correctly on the job, and the HVAC-to-5537 reassignment makes accurate role records especially important.

Because 5183 is searched as "5183 workers comp code" or "plumbing class code" by contractors who need a rate quickly to bid, it is tempting to treat it as a single number — but the rate is filed per state, and dual-wage and independent-bureau rules change the comparison in several states. Confirm the state's adopted plumbing classification and whether 5537 HVAC applies before assuming all field payroll lands in 5183.

For quote shoppers, the rate table on this page is a benchmark, not a binding quote. The filed base-rate estimate still changes after payroll, the carrier's loss-cost multiplier, experience modification, schedule credits, minimum premium, and any audit split to 5537 HVAC, a fire-sprinkler, sewer, gas-main, boiler, or excavation classification.