About The MAHC Current Edition

At a glance

The most recent version of the Model Aquatic Health Code (MAHC), the 4th edition, was posted in 2023. Links to the document, as well as a list of changes from the previous edition (2018) can be found below.

Thumbnail image of the Model Aquatic Health Code 2023 cover which shows people of different ages and ethnicities doing various activities in pools.

The 2023 Model Aquatic Health Code

2023 MAHC (4th Edition)--Posted 02/01/2023

To use a full database-driven search function for the MAHC, including the ability to pull the MAHC Code and Annex up at the same time, visit the Council for the Model Aquatic Health Code's (CMAHC) Search the MAHC page.

A track changes version of the 2023 MAHC (4th Edition) Code and Annex can be used to see what changes were made to the 2018 MAHC (3rd Edition) to create the 2023 MAHC.

Key Changes Found in the 2023 MAHC

This short list is a high-level summary only. Please consult the track changes version of the 2023 MAHC (4th Edition) to review all changes.

  • Layout
    • Deleted preface and user guide. Any of this content that is not already on CDC's MAHC website will be added.
    • Made glossary of abbreviations chapter 1, glossary of terms chapter 2, and list of cited standards and laws chapter 3.
    • Moved floatation tank–specific text to chapter 7 in both the MAHC Code and Annex.
  • Chapters 1–3
    • Synced content of glossary of abbreviations, glossary of terms, and list of cited standards and laws in MAHC Code and Annex.
  • Chapter 4
    • Increased the minimum water depth from 4 to 6 feet for starting platforms in new construction (
    • Established a maximum vertical clearance at the bottom of an aquatic venue or facility enclosure (no more than 2 inches above non-solid grade and no more than 4 inches above solid grade) (
  • Chapter 5
    • Decreased minimum pH of aquatic venue water from 7.2 to 7.0 (
  • Chapter 6
    • Established cyanuric acid to DPD–free chlorine concentration ratio greater than 45:1 as a closure item (
  • Resources
    • Deleted the alphabetical list of references, so references appear only in the order they are cited.
    • Created an EndNote library for the references.

Change Requests for This Edition

The MAHC update cycle includes the chance to submit change requests to CMAHC. For the 2023 edition, 530 change requests (CRs) were submitted to the CMAHC. Nine were withdrawn.

Of the 521 remaining CRs, the CMAHC Technical Review Committee voted to pass 320 (61.4%) and abstained on 21 (4.0%). CMAHC members voted to pass 326 (62.6%) of the 521 CRs. For the 500 CRs the CMAHC Technical Committee voted on, CMAHC members voted the same way on 498 (99.6%). The CMAHC Board of Directors recommended CDC accept 322 (61.8%) CRs. The Board's recommendations agreed with CMAHC member voting results on 513 (98.5%) of the 521 CRs.

Correspondence between the CMAHC and CDC on suggested changes to the MAHC is posted below.

Earlier Editions

All previous MAHC editions are replaced by the latest and most current edition of the MAHC and are archived on the Previous MAHC Editions page. All of the information related to the development of the MAHC can be found on the Creating the MAHC page.