Pool Keeper

Test your water, type in the numbers, and Pool Keeper tells you exactly how much of what to add. Not "alkalinity is low" — "Add 1 lb 2 oz baking soda".

Every reading and every calculation is free. There is no paid tier of the chemistry.

WHAT IT TRACKS

Free chlorine, pH, total alkalinity, calcium hardness, cyanuric acid, salt, borates and water temperature — plus CSI, the Calcium Saturation Index, worked out for you from the rest.

Track only what you actually test. Turn off the rest, and set your own min, target and max on anything where you disagree with the defaults.

WHAT IT TELLS YOU TO ADD

• Liquid chlorine, or trichlor by weight

• Soda ash to raise pH, muriatic acid to lower it

• Baking soda for alkalinity

• Calcium chloride for hardness

• Stabilizer, in both liquid and dry amounts

• Salt, and borax for borates

Doses are sized for your pool's volume, in US gallons, litres or imperial gallons, and given in pounds and ounces or grams and kilograms.

Buying the diluted 14.5% muriatic acid rather than the usual 31.45%? Set the strength once, and every acid dose is sized for the bottle you actually own.

BUILT AROUND YOUR POOL

Set the surface — plaster, tile, stone and pebble; vinyl; or fiberglass — and your chlorine source, and the target ranges move to match. A salt cell shifts the calcium and CYA bands. Vinyl brings calcium down.

Look after more than one pool? Each gets its own volume, surface, chlorine source and targets.

SEE WHERE IT IS HEADING

Chart any reading against its acceptable band and its target line, so you can see a slow drift before it becomes a problem. Scroll back through every test you have ever logged.

THE REST

• Tick doses off as you add them — retest and the list starts fresh

• Tap any chemical to read what it does and why it matters

• Set how often you test and it works out the date the next one is due

• Light and dark themes that follow your phone

• Real tablet layouts, not a stretched phone screen

• The screen stays awake while you are entering readings at the water's edge

Start logging straight away — no account needed. Sign in with Google when you want your pools backed up and synced across devices, and everything you logged beforehand comes with you.