Plumbing Services

Colorado requires every plumber working in the state to hold a current state-issued license — Apprentice, Residential, Journeyman, or Master Plumber — issued by the Colorado Department of Regulatory Agencies (DORA) State Plumbing Board. Commercial plumbing work requires at minimum a Journeyman supervised by a Master, and the contracting company must hold a Colorado Plumbing Contractor license. Verify both the company license and the on-site Master at the DORA license-lookup before signing — DORA publishes individual and company licenses in a public database. Local AHJs (Denver, Aurora, Boulder, etc.) may also require a contractor registration on top of the state license.

Nearly all commercial plumbing work in Colorado requires a permit from the local Authority Having Jurisdiction (AHJ) — the city or county building department where the property sits. Like-for-like fixture replacement (swapping a same-size faucet or toilet) is sometimes permit-exempt under the adopted plumbing code, but anything that alters the water supply, drain-waste-vent (DWV), gas, sewer service, or backflow assembly requires a permit and rough/final inspections. The contractor pulls the permit under their state license; the property owner is responsible for keeping a copy of the closed-permit record for any future sale, refinance, or tenant turnover.

Commercial plumbing differs from residential in scale, fixture demand, code requirements, and inspection cadence. Commercial fixture units are calculated per IPC commercial-occupancy tables, drain and vent pipe sizing is larger, and most commercial buildings have grease interceptors, backflow preventers, and floor drains that homes do not. Inspectors look for accessible cleanouts, grease-waste manifold separation, hot-water mixing valves for ADA compliance, and current backflow test reports — items that do not apply to single-family homes. Most commercial projects also involve gas piping, fire-suppression interlocks, and stormwater management that require specialty subcontractors.

Backflow prevention is required by Colorado plumbing code and by every Colorado water utility's cross-connection control program — the local utility (Denver Water, Aurora Water, etc.) keeps a public list of approved devices. Commercial buildings typically need a Reduced Pressure Zone (RPZ) assembly on the main, a Double-Check Detector Assembly (DCDA) on the fire line, and sometimes Pressure Vacuum Breakers (PVB) on irrigation. Once installed, every assembly must be tested annually by a certified backflow technician, with the test report filed to the water utility. Missing or failed tests can trigger water-service shutoff under most utilities' programs, so keep the annual test schedule current.

Grease interceptor sizing in Colorado is set by IPC commercial fixture-unit tables, the local sewer authority (e.g., Metro Water Recovery, Denver Wastewater), and the food-service occupancy classification. Small under-sink hydromechanical grease interceptors (HGIs) are sized in gallons per minute (GPM) per fixture and work for limited-menu prep areas. Larger external gravity grease interceptors (1,000 to 3,000+ gallons, in-ground) are required for full-service restaurants, multi-tenant food courts, and any operation that exceeds the local HGI threshold. The sewer authority's plan review confirms the sizing before the permit is issued; never order or install a grease interceptor without that approval letter.

For most commercial plumbing scopes, only the specific fixtures or zones being worked on need to be isolated — branch work, single-fixture installations, and many subscope changes can be done with the rest of the facility wet. A full service-line replacement, water-heater swap on the main, or backflow assembly replacement requires a partial or total water shutoff, usually scheduled after hours, overnight, or over a weekend to minimize tenant disruption. Temporary bypass or jumper hoses can keep critical fixtures (life safety, food prep, restrooms) wet during the cutover when downtime is not acceptable. Plan the shutoff window early because the local water utility has its own scheduling lead time for meter and tap work.

Denver Water owns the service from the main to the tap; the property owner owns from the tap inward, including the meter pit and meter. When a service is upsized (for example, from a 3/4-inch residential tap to a 1.5-inch commercial tap), Denver Water charges a tap fee that scales with the new tap size and the System Development Charge schedule in effect on the contract date. The customer also pays for the contractor's excavation and reconnection work on the building side. Get the Denver Water (or your local utility's) tap fee quote in writing before the bid — it can be a five- or six-figure line item on larger commercial upsizes.

Verify three things before signing a commercial plumbing contract: the contracting company holds an active Colorado Plumbing Contractor license (DORA lookup), the on-site Master Plumber is named on the company's license, and the company carries adequate commercial liability and workers-comp insurance for the scope of work. Ask for three recent references on projects of similar scale and request the closed-permit record for one of them. For grease, backflow, or medical-gas scopes, also confirm the technician certification specific to that work. Avoid any contractor who suggests skipping the permit, who quotes a service line replacement by phone without an in-person camera inspection, or who cannot name the on-site Master Plumber for your project.