Reason for Credential: Except as provided under s. 145.06 (4) Stats., and pursuant to s. 145.06, Stats., no person may install plumbing unless the person holds a credential issued by the department as a licensed master plumber, licensed master plumber-restricted, licensed journeyman plumber, licensed journeyman plumber-restricted, registered plumbing apprentice, registered plumbing learner-restricted, registered utility contractor or registered pipe layer. Requirements of Credential: The plumbing activities that may be undertaken by a person who holds a credential as a licensed utility contractor or registered pipe layer shall be limited to the installation or modification of water services, private water mains, sanitary building sewers, storm building sewers and private interceptor main sewers. A person who holds the credential shall carry on his or her person the credential issued by the department while performing or conducting the activity or activities permitted under the credential. Pursuant to s. 145.07 (11), Stats., a person who holds a credential as a registered pipe layer may install or modify water services, private water mains, sanitary building sewers, storm building sewers, or private interceptor main sewers under the general supervision of a licensed utility contractor, licensed master plumber, or a licensed master plumber-restricted service. Qualifications for Credential: A person applying for a pipe layer registration to install plumbing shall be at least 18 years old.