What Is the Model Aquatic Health Code?
The MAHC is the CDC's framework that states and local health departments use to write their own pool and spa regulations. It's not federal law, but it's the backbone of how most state codes are written. When the CDC updates the MAHC, states typically adopt those changes within 18 to 36 months.
The 2025 edition includes stricter guidance on water disinfection, sampling protocols, and record-keeping. It also clarifies operator certification requirements and adds new guidance for hybrid circulation systems.
Major Changes in the 2025 MAHC
1. Tighter Free Chlorine Standards
The 2025 code maintains the 1 to 3 ppm free chlorine minimum for most pools, but it adds stricter language around what "continuously available" means. You can't rely on a morning test to cover the afternoon. Water must be tested at least twice per day for commercial pools, and more frequently if automated monitoring isn't in place.
This change matters because it shifts some facilities toward continuous monitoring systems. If you're testing manually, you need to establish a testing schedule that covers peak hours. Most state codes are expected to mirror this language within two years.
2. Enhanced Disinfectant Residual Monitoring
The new code requires documented, tamper-evident testing. If you're writing free chlorine levels on a clipboard, you'll need to upgrade to a digital system or printed log that's harder to falsify. This is a direct response to violations where facilities were falsifying records.
Cyanuric acid rules also tightened slightly. The maximum stabiliser level drops from 100 ppm to 90 ppm for outdoor pools, which means you'll need more aggressive dilution and replacement practices during peak summer months.
3. New Guidance on Emergency Disinfection
The 2025 code adds a new section on what to do when a pool loses disinfectant residual unexpectedly. Previously, facilities had to close the pool. Now there's a 30-minute grace period if you can restore proper disinfection quickly. You can't use this to stay open longer, but it gives you time to react if a feeder fails or a line clogs without an immediate closure notice.
4. Operator Certification Requirements
The MAHC now explicitly states that each shift operating a commercial pool must have a certified operator on-site or available within 15 minutes. Most states already required this, but the new language is clearer about what "available" means. You can't leave the pool unattended while someone with a CPO runs an errand. The operator must be physically present or reachable to respond immediately to a chemical emergency.
5. Digital Record-Keeping and Cloud Backup
The 2025 code acknowledges that digital systems are standard practice. It includes new requirements for data security, automatic backup, and audit trails. If you use a pool management app or system, it must timestamp entries, prevent retroactive editing, and keep a backup copy off-site.
What This Means for Your Facility
If your state is already following the MAHC closely, you may already meet these standards. If your state code is older, you have time to prepare. Most states won't adopt these changes until 2026 or 2027. Use this window to audit your current practices.
Start by checking your testing frequency. If you're testing once a day, move to twice. If you're not sure whether your disinfectant system is "continuously available," it's not. Upgrade to automation or increase manual testing frequency. Review your record-keeping system. If it's a clipboard, consider digitising.
The certified operator requirement is straightforward. Someone with a current CPO needs to be on-site during all operating hours. If you're not yet certified, getting your CPO becomes even more important for career advancement in hospitality.
Frequently Asked Questions
Q: Will my state enforce the 2025 MAHC right away?
A: No. States adopt MAHC updates on their own timeline, usually 18 to 36 months after publication. Check with your state health department to see when they plan to adopt the 2025 version. Most likely, you have until 2027 before it becomes enforceable law.
Q: Does "continuously available disinfectant" mean I have to test every hour?
A: The MAHC specifies at least twice per day for most commercial pools, but high-traffic venues (water parks, hotel pools during summer) may be required to test more frequently. Your state regulations and local health department can clarify the exact schedule for your facility.
Q: If cyanuric acid drops to 90 ppm instead of 100 ppm, how much more chlorine will I need?
A: Slightly less. Lower stabiliser means your free chlorine is more active, so you'll use slightly less total chlorine. The tradeoff is you'll need to replace the water or dilute more often during summer months. The difference is small but meaningful over a season.
Q: Does my CPO need to be updated for 2025 MAHC changes?
A: Not immediately. Your CPO doesn't expire when a new MAHC is published. However, any CEU or renewal courses will include the new standards. If your CPO expires before your state adopts the 2025 MAHC, you'll learn the new rules during recertification.
Ready to stay ahead of compliance changes? CPO PRO offers Certified Pool Operator training every two weeks, and we're already integrating 2025 MAHC updates into our curriculum. Book your class today.
Ready to Get Your CPO Certification?
CPO PRO offers PHTA-certified CPO courses in Las Vegas, virtually over Zoom, and on-site at your facility. One test day. Five-year certification. $435 all-inclusive.
See Upcoming Test Dates