Iowa Code § 105.21: Reciprocal licenses.

The board may license without examination a nonresident applicant who is licensed under plumbing, mechanical, HVAC-refrigeration, sheet metal, or hydronic professional licensing statutes of another state having similar licensing requirements as those set forth in this chapter and the rules adopted under this chapter if the other state grants the same reciprocal licensing privileges to residents of Iowa who have obtained Iowa plumbing or mechanical professional licenses under this chapter. The board shall adopt the necessary rules, not inconsistent with the law, for carrying out the reciprocal relations with other states which are authorized by this chapter.