Pool, Spa & Water Treatment Chemistry calculator
Combined Chlorine Breakpoint Calculator
Estimate the free-chlorine increase required for breakpoint treatment from combined chlorine, the selected multiplier, and an efficiency correction for your treatment conditions.
What this calculator does
- Estimate breakpoint oxidation demand from combined chlorine, a breakpoint multiplier, and delivery efficiency.
- Use it to plan breakpoint chlorination after confirming combined chlorine and facility policy.
- Turns combined chlorine and a multiplier into an estimated free-chlorine dose needed for breakpoint treatment.
Formula used
- Breakpoint demand = combined chlorine x breakpoint multiplier x efficiency correction x safety buffer
Inputs explained
- Combined chlorine reading: Use total chlorine minus free chlorine from a reliable test.
- Breakpoint multiplier: Many planning references use 10x combined chlorine for breakpoint.
- Delivery efficiency correction: Enter 100 divided by delivery efficiency percent. For 90% efficiency, enter 1.11.
- Safety buffer factor: Use 1.0 for standard dose. Increase only for severe chloramine events or heavy organic load.
How to use the result
- Use it when planning breakpoint chlorination after confirming combined chlorine with a reliable test.
- Keep pool closed to bathers during breakpoint treatment. Reopen only after free chlorine drops below 3 ppm or the site code threshold and retesting confirms clearance. Never mix chlorine products together before adding. Use the result for planning math only. Follow product labels, health codes, local regulations, test-kit instructions, chemical safety rules, and qualified pool operator guidance before dosing water.
Common questions
- What is the combined chlorine breakpoint calculator for? Estimate breakpoint oxidation demand from combined chlorine, a breakpoint multiplier, and delivery efficiency.
- What numbers do I need for combined chlorine breakpoint? You need combined chlorine reading, breakpoint multiplier, delivery efficiency correction, safety buffer factor. Use measured test results and the same pool, spa, tank, or treatment volume for every input.
- How should I use the result? Use the result to check dose size, run time, flow, inventory, or operating cost before changing a treatment plan or purchase order.
- What should I verify before acting? Verify water volume, units, chemical strength, product label directions, bather load, local code, and current test results. Retest after treatment and never mix incompatible chemicals.
Last reviewed 2026-05-12.