"Master plumber" means "master plumber" as defined in RSA 153:27I, XI, namely "any person, firm, corporation, or limited liability company that, as a business, hires or employs a person or persons to do plumbing work, or, without hiring any person, does that work as a principal business or as auxiliary to a principal business for its own account."
N.H. Admin. Code § Saf-Mec 102.18