(1) It is unlawful for any person to engage in the business, trade, or work of installing, removing, altering, or repairing plumbing and drainage systems or parts of plumbing and drainage systems without first obtaining a permit from the department of labor and industry.
(2) A separate permit must be obtained for each building or structure.
(3) A person may not allow any other person to do or cause to be done any work under a permit secured by the permittee except persons in the permittee's employ.
(4) When a permit has been obtained to connect an existing building or existing work to the public sewer or to connect to a new private disposal facility, backfilling of private sewage disposal facilities abandoned consequent to the connection is included in the permit.