No person shall construct, remodel, alter, enlarge, nor install any sewage disposal system or part of any sewage disposal system, or engage in the business of soil percolation tests unless he is in possession of a valid license issued by the Health Officer. There shall be a separate license for contractors and testers. The issuance of one (1) license shall not entitle the licensee to engage in the other licensed activity. The applicant shall verify in writing that he will install sewage disposal systems or conduct percolation tests according to these regulations and/or approved plans. Applicants shall also, at the discretion of the Health Officer, be required to complete a written examination and/or oral review to indicate the applicant's knowledge of the pertinent parts of this Subtitle and applicable State laws and regulations. Homeowners installing their own sewage disposal system are exempted from licensing requirements, but the Health Department must stake out the exact location of the disposal system prior to installation.