Breakpoint Chlorination Dose
The combined chlorine in the water, and the shock dose that burns it off.
Example
You enter
- Total chlorine (ppm) 1.5
- Free chlorine (ppm) 1
- Breakpoint ratio (default 10) 10
- Pool volume (gallons, optional) 15000
- Product available chlorine (%, optional) 65
You get
- Combined chlorine (chloramines) 0.50 ppm
- Breakpoint free-chlorine dose 5.0 ppm
Checked against published worked examples from: Indiana Department of Health.
Details, formula, and sources
ScopeCombined chlorine (chloramines) = total - free, and the breakpoint shock dose = ratio x combined (commonly 10:1). Total 1.5, free 1.0 -> 0.5 ppm combined, a 5 ppm shock; shock past breakpoint (a partial dose worsens it). The label and testing govern.
Formula or tablecombined = total - free; dose_ppm = ratio x combined (ratio ~10); optional lb_product = dose_ppm x (gal/1e6) x 8.34 / (avail/100).
Source and editionThe breakpoint (superchlorination) chlorination rule and Standard Methods 4500-Cl, by name.
Free accessThe breakpoint-curve behavior and the ~10:1 shock rule are published free by pool-care and water-treatment references (Standard Methods 4500-Cl). The product label and testing govern.
What governsEstimate. AHJ and licensed professional govern.
API field namestotal_ppm, free_ppm, ratio, gallons, avail, combined_ppm, dose_ppm
- Combined chlorine combined = total - free; dose = ratio x combined (ratio ~10)breakpoint curve / Standard Methods 4500-Cl
- Shock past breakpoint a partial dose below breakpoint worsens chloraminespool-care practice
- Confirm by testing 10:1 is a rule of thumb; confirm the breakpoint by testing; no baseline demand addedscope of this tile