At Class A / Class 4, Regulation 100 is not a rule you comply with — it's a framework you're expected to be able to apply to edge cases other operators bring to you, and to explain to owners, inspectors, and boards when a classification is disputed. This guide goes to full technical depth on how classification actually works and on exactly which bodies hold the legal authority behind the regulation.
The Water Treatment Classification Matrix, Fully Worked
Regulation 100 § 100.4 classifies water treatment facilities using a matrix crossing plant design flow rate against treatment process, not a cumulative point system. The flow bands are:
- Less than 350 GPM
- 350 – 1,400 GPM
- Greater than 1,400 GPM
Each recognized treatment process — disinfection alone, filtration, membrane treatment, and other listed technologies — maps to a specific class outcome within each flow band un