Md. Code, Business Occupations and Professions § 12–206

(a) A county shall:

(1) enforce the State Plumbing Code; or

(2) adopt and enforce a local plumbing code that meets or exceeds the minimum standards of the State Plumbing Code for the proper design, acceptable installation, and adequate maintenance of plumbing systems.

(b) (1) In this subsection:

(i) “greywater” means used, untreated water generated by:

1. a clothes washing machine;

2. a shower; or

3. a bathtub; and

(ii) “greywater” does not include water from:

1. a toilet;

2. a kitchen sink; or

3. a dishwashing machine.

(2) A county may not adopt or enforce a provision of a local plumbing code that prohibits a system that recycles greywater, as authorized under the State Plumbing Code.

(c) Unless the Board determines that a county is adequately enforcing the State Plumbing Code or a local plumbing code that meets or exceeds the minimum standards of the State Plumbing Code, the Board shall enforce the State Plumbing Code in that county.

(d) The Board may make a cooperative agreement with a county for the county to enforce:

(1) the State Plumbing Code; or

(2) if the county has adopted a local plumbing code, that code.