The Model Aquatic Health Code (MAHC)

When you consider the public health threats that are presented by commercial and public pools, it is not surprising to find that Model Aquatic Health Code (MAHC) was created by the U.S. Centers for Disease Control (CDC). The Model Aquatic Health Code (MAHC) is a guidance document that helps local and state authorities, as well as the aquatics sector, to make swimming and other water activities healthier and safer. States and localities can use the MAHC to create or update existing pool codes to reduce risk for outbreaks, drowning, and pool-chemical injuries. The MAHC guidelines are all-inclusive and address the design, construction, operation, maintenance, policies, and management of public aquatic facilities.

What the MAHC Says About Secondary Disinfection Systems

MAHC language specifically states, “Due to the risk of outbreaks of Recreational Water Illnesses (RWI’s) associated with sanitizer-resistant pathogens such as Cryptosporidium and Giardia, it is strongly recommended that all aquatic facilities include Secondary Disinfection Systems (SDSs) to minimize the risk to the public associated with these outbreaks.” The MAHC goes on to state, “However, there are specific types of facilities that pose a greater risk to bathers, and therefore, Secondary Disinfection Systems are required for: therapy pools, wading pools, swim school pools, and aquatic play facilities/features.” According to the MAHC the following conditions must be met for all Secondary Disinfection Systems (SDSs).

• All SDSs must be certified by an ANSI-Accredited third-party testing and certification organization to verify that they provide the minimum inactivation of Cryptosporidium parvum in the full flow.

• All SDSs must provide a minimum of 3 log (99.9%) inactivation of Cryptosporidium parvum in the full flow, prior to return of the water to the pool or aquatic feature at the minimum turnover rate.

• Ozone systems and UV systems are approved SDSs.

Ozone Secondary Disinfection Systems Must be Properly Sized

All ozone systems must be sized in accordance with the MAHC. Undersized ozone systems will not be recognized as MAHC compliant. Only ozone systems that are certified by an American National Standards Institute (ANSI)-Accredited third-party testing and certification organization to verify that they provide a 3 log (99.9%) inactivation of Cryptosporidium parvum in the side-stream applied full flow are qualified to be an SDS. This standard is in addition to the current ANSI/NSF Standard 50.

DEL recognizes the MAHC, and ensures all ozone systems for aquatics are 100% MAHC-compliant.


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