The short answer
An automatic chlorinator dissolves trichlor tablets at a rate you set, keeping chlorine steadier than adding it by hand. In-line models plumb directly into the return pipe; off-line models connect with small tubes beside it, which suits tight pads. Always install them after the heater.
Options we cover
Off-line: Hayward CL200; in-line: Pentair Rainbow 320.
Tablets and stabilizer
Trichlor tablets add cyanuric acid (stabilizer) as they dissolve. Test CYA every few weeks; when it climbs too high, partial draining is the usual fix.
SafetyNever mix tablet types or put other chemicals in a chlorinator; incompatible chemicals can react violently.
Products mentioned
Questions readers ask
Where should a pool chlorinator go?
After the filter and after any heater, so concentrated chlorine doesn't pass through equipment it can corrode.
Can I use a chlorinator with a salt system?
You don't need one; a salt system makes chlorine.