1–3 ppm is the sweet spot.

Keep your free chlorine between 1 and 3 parts per million. That’s enough to kill bacteria and algae without turning the pool into a bleach bath.

The exact number depends on your stabilizer (cyanuric acid). If you use tabs with CYA, you might need to run closer to 3 ppm. If you use liquid chlorine with little or no CYA, 1–2 ppm can be fine. But for most backyard pools with standard pucks, 2–3 ppm is the target.

Testing once a week is plenty unless you’ve had heavy use or a storm. If it drops below 1, bacteria start partying. Above 4–5, you’re just burning through money and irritating eyes.

That range works for almost everyone. Skimping on the low end is the only real risk.