Total chlorine
Definition
Total chlorine is free chlorine plus combined chlorine added together. Most test strips report total chlorine instead of free chlorine, so a pool full of chloramines can look chlorinated on a strip while the true free chlorine is near zero.
Why it matters
Total chlorine is useful for one thing: the difference between it and free chlorine is combined chlorine, the spent chlorine that smells and stings. On its own the total tells you nothing about whether the water is sanitized. If a strip or a pool store says your chlorine is fine and the water is still green or cloudy, this is one of the two usual reasons, along with high CYA. A drop-based FAS-DPD kit reads free chlorine separately from combined, which is the reading you can act on.