No firm, association or corporation shall be registered as a contracting plumber unless the proper officers of the concern shall certify to the chief building official that an identified master plumber, licensed under the provisions of this section, is an officer, member or regular employee of such concern, and that such master plumber will be in direct supervision of all of the plumbing work contracted and done by such concern, and unless such concern has in force and effect one or more insurance policies as required by §26-41 below.