poolcntrl
Cntrl your pool with confidence.
How poolcntrl works
Everything else got easier. Now your pool does too.
Test your water
Snap your test strip, or type the numbers in.
Snap your pool
Photograph the water. poolcntrl names what it sees and what to check next.
Follow your steps
Exact amounts for your pool’s size, surface and the chemicals in your garage. Jugs and cups, not chemistry.
Let it watch
Weather, trends and reminders between tests, so the next problem is one you saw coming.
Confidence, not chemistry.
Exact, not approximate
Same readings, same answer, every time. Where a dose comes from a formula, we show you the formula.
Yours, not generic
Sized to your pool’s volume and surface, and to the chemicals already in your garage.
AI reads, chemistry decides
AI reads your strip and looks at your water. The chemistry engine decides every amount.
See it work.
The real engine on a sample pool. Change any number and the plan changes with it.
Your pool
Water test
Your plan
What to look for on the label: Liquid chlorine
- Sodium hypochlorite — the name on the ingredient panel
- Chlorinating liquid, pool chlorine, liquid shock
- Plain unscented household bleach is the same chemical, weaker
- 10% and 12.5% sodium hypochlorite are the two pool-store jugs
- 6% to 8.25% for household bleach
- 1-gallon jugs, usually sold in a case of two or four
- 2.5-gallon jugs, which pool stores often stack by the door
- Unscented household bleach with no thickeners, scent or splash-less additive
- Cal-hypo does the same job as a powder, but leaves calcium behind
Check the strength on the front and the date on the jug. Liquid chlorine weakens on the shelf, so the freshest case is worth reaching for. The app asks which strength you bought, and the amount it gives you changes with your answer — so tell it the jug you actually own, not the one it assumed.
Your water is balanced.
Saturation (LSI): 0.0
Your pH, alkalinity, calcium and water temperature are in balance — the water is neither pulling calcium out of your pool nor dropping it onto surfaces.
This matters most on plaster, pebble and tile pools, and on saltwater pools — plaster has calcium the water can take, and a salt cell is usually the first thing to scale up. Vinyl and fiberglass shells are much less sensitive to it.
⚠️ Don't just watch the clock — retest before swimming. Water is safe when free chlorine is between 3 and 10 ppm and pH is 7.2–7.8.
Re-test in about 4 hours.
Here is the whole calculation behind that amount — your pool’s volume, how far the reading has to move, and the strength of the product.
18,000 gal × 3 ppm ÷ 10% → 69 fl ozThat dose is real — the same deterministic engine the app runs, same answer every time.
And when the numbers cannot be right — total chlorine under free chlorine, a pH no pool has — poolcntrl says so instead of dosing. Nothing gets rounded into an amount.
Pro already knows your pool, so you skip every field above — and checks your next test against the chlorine you add.
Engine ruleset mvp-seed-v1.23.0
Pro knows your pool.
After your free two weeks, Pro is $5.99 a month or $49.99 a year.
The alternative is free, and it is a fair one — your pool store will read a sample on Saturday. Why pay for this instead →
New to this? Start here.
Plain-language guides, written for first-time owners.
Start your free trial.
Two weeks with everything unlocked — no credit card. After the trial it’s $49.99 a year, or the free calculator forever.
poolcntrl sets up in the iPhone app. This form creates the account; the site is the read-only view of what the app records.
Download poolcntrl now
Take your pool’s perfect routine with you. Free to start on iPhone — Android is on the way.
On Android?The full chemistry engine runs free in your browser — the same server-side math the iPhone app asks for, and the same answer. No app to install, no account needed.Open the free calculator →One subscription, every device — phone at the pool, laptop at the kitchen table.