The pool and hot tub app that tells you what to add
Test your water, type in the numbers, and the app tells you what to add from the products you already have, how much, in what order, and when you can swim again, per the product label. Pool or hot tub. No account. In development for iPhone.
What the app does in 30 seconds
- Tell it about your water once: pool or hot tub, and how many gallons. Pick your Intex, Bestway, or Coleman model to use the manufacturer's capacity, or measure a pool of any shape.
- Enter a test from strips or a drop kit.
- Get a plan: numbered steps with exact amounts for your products ("58 fl oz of pool chlorine 10%"), waits between chemicals, and a clear "Don't swim yet" when needed.
- Log it: tap "Mark as Added," and the app keeps your history and reminds you when to retest.
It uses the same tested chemistry engine as every calculator on this site, so the site and the app never give you two different answers.
Add chlorine
58 fl oz1.70 L
Pool liquid chlorine 10%
FC 1 → 4 ppm
Wait 30 min with the pump running.
Raise alkalinity: add baking soda
4.2 lb1.91 kg
Baking soda
TA 70 → 90 ppm
Wait 30 min with the pump running.
Lower pH: add acid
13 fl oz393 mL
Muriatic acid 31.45%
pH 7.8 → 7.5
No account, no brand pushing, works offline
- Open it and start. There is no sign-up screen between you and your first dose.
- It never tells you to buy a specific brand. Doses are based on the active ingredient and the percent on your label, so the jug from any store works.
- Everything runs on your iPhone, with or without a cell signal at the pool.
Any test strips or drop kit: fast manual entry
Strip scales differ by brand, and phone cameras struggle with wet pads and changing light. So typing in your results is the main way to enter them, not an afterthought. Tap the step that matches your strip, or enter exact numbers from a drop kit. When you enter strip steps, the app shows a range instead of claiming more precision than the strip has.
Hot tub mode from 50 gallons
Hot tubs get full support: 50–1,500 gallons, chlorine or bromine, doses in teaspoons and grams, drain-and-refill reminders, and no stabilizer by default, as the CDC recommends. More on the hot tub care pages.
History charts and reminders
Every test and every dose goes into a log you can scroll back through. Charts show each reading against its target range, with markers where you added chemicals, so you can see what actually worked. Reminders are local notifications on your phone: test days, retests after a dose, and filter or salt cell chores.
Free vs Plus: what's included
| Feature | Free | Plus |
|---|---|---|
| All dose calculations, pool or hot tub | Yes, for 1 pool or hot tub | Yes, unlimited pools and hot tubs |
| Volume calculator and pool models | Yes | Yes |
| Test and dose log | Last 30 days | Full history |
| iCloud sync across your devices | Yes | Yes |
| Reminders | Basic (test days, retests) | All |
| Charts | Last 2 weeks | Full history, compare readings |
| Export | CSV of all data | Adds PDF report |
| Home Screen widgets | 1 small widget | All sizes |
Dose calculations are never behind a paywall. Planned U.S. prices for Plus: $24.99 a year with a 14-day free trial, $14.99 for a 6-month Season Pass that does not renew, or $59.99 once for Lifetime. There is no monthly plan: pool care is seasonal, so the Season Pass covers one swim season without a renewal. You can cancel a subscription from your iPhone's subscription settings in a few taps. Prices outside the U.S. are set by the App Store in local currency. Renewal, the free trial, cancellation, and refunds are explained in our subscription terms.
Privacy: data stays on your iPhone and iCloud
No account means we don't have a database of users. Your pools and tests live on your device and in your private iCloud, where we can't read them. No ads, no third-party tracking. Details in our privacy policy. Like this site, the app puts your product's label first: see chemical safety and product labels.
FAQ
Is the app free?
Yes. Dose calculations for one pool or hot tub, the last 30 days of your test log, and basic reminders are free. Plus adds more pools and hot tubs, your full history and charts, PDF export, and extra widgets: $24.99 a year with a 14-day free trial, $14.99 for a 6-month Season Pass that does not renew, or $59.99 once for Lifetime.
Do I need an account?
No. There is no sign-up. Your data syncs through your own iCloud if you use it.
Does it work with any test strips?
Yes. You type in what your strip or drop kit shows, so any brand works. Strip steps are shown as ranges, because strips read in steps.
Does it work for hot tubs?
Yes, from 50 to 1,500 gallons, with chlorine or bromine and small doses in teaspoons and grams.
Looking for something specific? Read how we compare in the best pool chemistry apps, see our Pool Math alternative page, or check how the numbers are calculated. Pool service tech? See our plan for solo techs.