The Illinois General Assembly has "declared" that individuals who plan, inspect, install, alter, extend, repair and maintain plumbing systems shall be individuals of proven skill.
Illinois drinking water supplies are protected by both the Illinois Environmental Protection Agency (IEPA) and the Illinois Department of Public Health (IDPH).
In the case of a residential or commercial irrigation system, a reduced pressure principle backflow prevention device (RPZ) is required between the potable water supply and the irrigation system.
The State of Illinois registers plumbing contractors and state law requires that anyone doing plumbing work in Illinois be registered with the State of Illinois or the City of Chicago.
The EPA under the Clean Air Act requires individuals working on refrigeration equipment, including residential air conditioning units, to be certified in the proper handling of "ozone-depleting" substances.