Operator terms · Water and wastewater
What is total chlorine?
Total chlorine is the sum of free chlorine and combined chlorine in the water. It is the whole amount of chlorine residual present, both the fast-acting free form and the slower, longer-lasting form bonded to ammonia. Operators use it to see the complete residual picture.
Last reviewed 2026-08-03
How the parts add up
Free chlorine is the available, unreacted form. Combined chlorine is bonded to ammonia as chloramine. Add the two together and the result is total chlorine, the full residual in the sample.
Why measure all three
Comparing total to free tells an operator how much of the residual is combined. That balance matters because free chlorine disinfects faster while combined chlorine holds longer in the distribution system.
Common questions
- What makes up total chlorine?
- Free chlorine plus combined chlorine added together.
- Is total chlorine the same as the dose?
- No; the dose is what was added, total chlorine is the residual left.
- Why compare total and free?
- The difference shows how much of the residual is combined chlorine.