The Model Aquatic Health Code, or MAHC (pronounced by many as MOCK), is the recreational aquatic industry's collective attempt to write the absolute best pool design and operational code (or set of pool operating rules, guidelines, procedures, design standards, etc.) based on research, expert input and committee and stakeholder collaboration. The MAHC is not legislation and swimming pools are not required to follow MAHC rules and recommendations, unless your state has adopted it as your official pool code. The end goal for many involved in the MAHC would be the formal adoption of the MAHC by all cities, counties, and states as their official local swimming pool health and safety regulations. Currently, pool codes vary drastically from state to state and even city to city. For example, several states have absolutely no pool code whatsoever, while others have a pool code that consumes hundreds of pages. Minimum disinfectant levels are different state to state. Some states require bacteriological testing, while others do not.
Local health departments may adopt none, all, or part of the MAHC to supplement or completely replace their current code. An example of a "full adoption" is the state of New Mexico, which made the bold move to adopt nearly the entire MAHC code as its official pool code several years ago. Several other entities have adopted parts of the code as well.
At a minimum, the MAHC is a great set of standards and guidelines that serves to provide pool operators with a framework of best practice guidelines. The MAHC is updated every two years with the most current version (3rd edition) published in 2018. For more information, see the links below.