"The Solar Rating & Certification Corporation (SRCC) recently developed the National Solar Heating and Cooling Product Certification Program, in short OG-400. Certification to OG-400 provides manufacturers proof of compliance for solar water heating systems and validates compliance with minimum requirements for safety and durability. Certified systems must properly integrate with pool designs and systems to ensure that critical safety protections for water quality, suction entrapment, and maximum temperature are maintained."
To read the full article: https://www.solarthermalworld.org/content/new-us-standard-solar-pool-and-spa-heaters