Chlorine is a member of the same chemical family as bromine. This chemical family known as halogens attacks microorganisms such as bacteria using oxidation and kills them. This is why chlorine and bromine are the two most popular choices for sanitizer in pools and spas.
Chlorine is the most commonly used primary sanitizer in swimming pools. Chlorine tends to be less effective than bromine at high temperatures like those in a hot tub when in tablet form and that is why it is not recommended as a primary sanitizer for hot tubs. If you do choose to use chlorine as your primary sanitizer or an occasional shock treatment, the granular form known as “sodium dichlor” is the best option for hot tubs. It is not excessively acidic or alkaline, and does not quickly deplete at higher water temperatures like the more concentrated version.
If you do choose to use chlorine granules as a primary sanitizer you would just want to be sure and test your water VERY often since it is not being dispensed automatically like bromine tablets or cartridges would be.
When testing your chlorine levels you are looking for a reading of 1.5 to 3.0 ppm (parts per million). Chlorine levels not being high enough could result in unsafe water conditions that can cause skin irritation, smelly water, and a growth place for bacteria.
No matter what form of sanitizer you choose to use in your hot tub maintaining it properly is the key to success, do this by testing often and making sure all your chemical levels are balanced.