If satisfied with the competency of such applicant, the appropriate board of plumbing examiners shall issue a certificate to such applicant, authorizing him to engage in the business of installing sanitary plumbing. The fee for the certificate to a master or employing plumber shall be five dollars and to a journeyman plumber two dollars. The certificate shall be valid for the term of one year, but it may be renewed upon proper application to the board which issued it and the payment of a fee of fifty cents.