Plumbing contractors are required to take out permits on jobs performed by their companies. The master plumber's signature is required on all permit applications. A contractor may not do work on a "homeowner" issued permit.
Homeowners may do their own plumbing installation on their residence if the following is true: the work is personally performed by the homeowner and the property is not for sale, resale, is not rental property, which is occupied or is to be occupied by tenants for lodging, either transient or permanent; and is not generally open to the public.
According to Colorado statutes, "plumbing" includes:
All potable water supplies and distribution piping
All plumbing fixtures and traps
All drainage and vent pipes
All building drains, and in health care facilities, all medical gas and vacuum systems
Manufactured / Modular / Mobile homes require a permit and inspections for the water / sewer and gas connections. In addition, new gas piping installation and gas piping conversions require permitting and inspections