The short version of pool care
If you read nothing else here, read this. A swimming pool needs four things, and they matter in this order:
Sanitizer, always. Chlorine is the only thing killing algae and pathogens. Circulation doesn't, filters don't, and "shock once a week" doesn't if the level falls to zero in between. A pool with chlorine in it and nothing else right will stay clear for weeks. A pool with everything else perfect and no chlorine turns green on schedule.
Stabilizer, matched to it. Cyanuric acid protects chlorine from sunlight, and in doing so decides how much chlorine you need — roughly 11% of your CYA reading. This single relationship explains most "I did everything right and it still went green" stories, because the pool store's 1–3 ppm advice ignores it.
pH, kept in a band. Between 7.2 and 7.8, for comfort and to stop the water attacking your surfaces. Alkalinity is what keeps pH from wandering, which is why the two are usually discussed together.
Calcium and the saturation index, occasionally. These decide whether your water slowly dissolves your plaster or coats it in scale. They move slowly, so they're a monthly thought rather than a weekly one.
That's it. Salt is only a delivery method for chlorine. Phosphate removers, clarifiers, enzymes and most of the rest of the shelf are treating symptoms of one of the four above being wrong.
What the week actually looks like
| How often | What you do | Time |
|---|---|---|
| 2–3× a week | Test chlorine and pH; add chlorine to target | 5 minutes |
| Weekly | Brush the walls and steps, empty the skimmer, check the filter pressure | 15 minutes |
| Every 2–4 weeks | Full test — alkalinity, CYA, calcium — and adjust what has drifted | 15 minutes |
| Seasonally | Open, close, and check the saturation index against the water temperature | An afternoon |
The full version, with the target numbers on it, is the printable maintenance schedule. A well-behaved pool is genuinely about twenty minutes a week. Pools that eat entire weekends are almost always pools that were allowed to fall below minimum chlorine at some point, and recovery costs far more time than prevention.
The mistakes that cause most problems
Guessing the volume. Every dose is proportional to it. A pool "about 20,000 gallons" that's really 15,000 gets a third too much of everything, forever.
Chasing a fixed chlorine number. There isn't one — it depends on your CYA. This is the single most consequential thing on the site, which is why it has its own guide.
Letting pucks run all season. Trichlor is convenient and adds stabilizer with every dose. A floater running from May adds enough CYA by August to make your chlorine functionally useless at the levels you're holding.
Trusting a strip during a crisis. Strips stop reading around 10 ppm, and shock levels start at 12 and climb. You cannot clear an algae bloom on readings you can't take.
Buying the solution before diagnosing the problem. Cloudy water has half a dozen causes and most bottles marketed at it treat one. Test first; the answer is usually chlorine or the saturation index, and both are free to fix if you already have the chemicals.