Keeping your pool chemistry balanced is the single most important thing you can do to protect your pool and keep it safe to swim in. Here's what to check and how often.
The 3 numbers that matter most
pH (target: 7.4 – 7.6)
pH measures how acidic or basic your water is. Too low and the water irritates eyes and skin. Too high and your chlorine stops working. Test this twice a week and adjust with pH Up or pH Down from any pool supply store.
Chlorine (target: 1 – 3 ppm)
Chlorine kills bacteria and algae. Too little and your pool turns green. Too much and it irritates skin and bleaches swimsuits. Test twice a week. Shock your pool once a week during heavy swim season.
Total Alkalinity (target: 80 – 120 ppm)
Think of alkalinity as the stabilizer for your pH. If your pH keeps swinging up and down, low alkalinity is usually the cause. Adjust with baking soda to raise it or muriatic acid to lower it.
Other things to check monthly
Calcium Hardness (target: 200 – 400 ppm) — prevents plaster from cracking. Cyanuric Acid (target: 30 – 50 ppm) — protects chlorine from burning off in sunlight. Total Dissolved Solids — if this gets too high, a partial drain and refill fixes it.
Tips
Test your water first thing in the morning before anyone swims. Buy a good digital test kit — test strips are less accurate. Take a water sample to your local pool store monthly for a full analysis — it's usually free.