Water Test Calculator, the app that finally gets pool chemistry right
The first consumer app to auto-calculate CYA-based chlorine targets, preventing chlorine lock before it happens. iOS and Android, ~10 days from launch.
Last updated: 2 June 2026
Water Test Calculator is a mobile application for iOS and Android that handles residential pool and spa water chemistry, testing, dosing recommendations, treatment planning, and history tracking, in one app. It launches in approximately 10 days.
This page is a complete reference to what the app does, what’s free, what’s premium, what makes it different from alternatives, and what to expect from the launch.
The single feature that makes Water Test Calculator different
Most consumer pool apps recommend a static “1–3 ppm free chlorine” target regardless of your cyanuric acid level. That recommendation is correct for a pool with zero CYA and dangerously low for a pool with 80+ ppm CYA. The full chemistry is in our chlorine lock guide, but in short, the active chlorine you actually need scales with CYA, and the right target is 11.5% of your CYA reading.
Water Test Calculator is the first consumer-facing app that does this calculation automatically. You enter your CYA reading once. From that point onward, every chlorine dose, every shock recommendation, and every “your pool needs X” alert in the app accounts for your stabiliser level. You don’t need to know the math, you don’t need to remember it, and you don’t need to look up the chart on a chemistry forum. The app holds it for you.
What the app handles
Three pool types in one app
- Chlorine pool testing, free chlorine, combined chlorine, pH, total alkalinity, cyanuric acid, calcium hardness. Full guided workflow.
- Saltwater pool testing, adds salt level tracking and SWG-specific recommendations. Works with all major cells (Hayward AquaRite, Pentair IntelliChlor, Astralpool VX, Zodiac TRi).
- Spa and hot tub testing, separate profile for tighter pH range, higher chlorine targets, faster turnover.
Two testing modes
Guided Mode walks you through every step in the right order, Total Alkalinity first, then pH, then chlorine. The app shows recommendations only after you’ve entered each reading, which prevents the common mistake of dosing based on imagined readings. Final step is a complete summary of all chemical additions you need to make, with wait times and safety warnings.
Basic Mode shows all inputs at once for experienced users. Enter readings, get dosing, done. Designed for the second-summer pool owner who knows the workflow.
Built-in calculators
- Pool volume calculator, rectangle, circular, oval, and kidney shapes, with the right correction factors. Stores result so you never re-enter your pool size.
- Shock calculator, auto-targets based on your CYA reading using the 10×CC or 40% of CYA rule (whichever is higher). Most other shock calculators ignore CYA entirely.
- Chemical dosing, precise calculations for liquid chlorine, cal-hypo, dichlor, sodium bicarb, muriatic acid, soda ash, calcium chloride, and cyanuric acid.
Smart notifications
The app schedules reminders based on the chemistry you’ve added. If you’ve shocked, it reminds you to re-test in 4 hours and again in 24. If you’ve added muriatic acid, it tells you the wait time before swimming. If your last test reading was below the safe sanitiser threshold, it’ll prompt you to re-test.
Volume memory
Pool volume is entered once and remembered forever. Every subsequent recommendation uses your pool’s actual volume, not a generic 100,000 L default that’s wrong for most pools.
Offline-first
Full functionality without an internet connection. Pool’s at the back of the property where Wi-Fi doesn’t reach? Doesn’t matter. Test, calculate, dose, log, all of it works offline.
Pricing
| Tier | Price | Free trial | What you get |
|---|---|---|---|
| Free | $0 | , | Core testing, all calculators, ad-supported. Test history limited to last 7 days. |
| Weekly | $6.99 | 3 days | Full premium, no ads, unlimited test history. |
| Annual | $79.99 | 7 days | Same as weekly, billed annually. Best value (works out to $1.54/wk). |
| Lifetime | $299.99 | , | One-time payment, premium forever. |
Our recommendation: start with the 7-day annual trial. That gives you a full week of premium during your normal pool-maintenance routine. If you maintain your pool yourself, the time saved on chemistry math typically justifies the $79.99 within the first month, and the lifetime tier works out to about 3.75 years of the annual subscription.
What’s launching at version 1.0
- Three pool types (chlorine, saltwater, spa)
- Guided + Basic testing modes
- Volume calculator (4 shapes)
- Shock calculator (CYA-targeted)
- Chemical dosing for all common pool chemicals
- Volume memory (per pool/spa)
- Smart wait-time notifications
- Offline-first architecture
- Unit toggle (metric/imperial)
- Free + Premium tiers via in-app subscription
Compatibility
- iOS: iOS 14 and above. iPhone and iPad supported.
- Android: Android 7.0 (API 24) and above.
- Web: Not currently available on web. Mobile-first design.
Privacy and data
Water Test Calculator is offline-first. Test readings, pool volumes, and chemistry history live on your device by default, they’re not sent to a server unless you opt into cloud sync (which is post-v1.1). The app collects standard anonymous usage analytics (which screens are used, crash reports) but no personally-identifying water chemistry data leaves your device unless you explicitly choose to.
How it compares to alternatives
The full comparison of 8 pool water testing apps is in our best pool apps roundup. The short version: Water Test Calculator is the only app that handles CYA-based chlorine targeting by default. Pool Math (the long-standing standard) does it manually if you know to do it. Most others don’t do it at all.
Sources & references
- Trouble Free Pool, ABCs of Pool Water Chemistry
- Richard Falk, The Chlorine/CYA Relationship
- ANSI/APSP-11, Water Quality Standards in Public Pools
- AS 3633-1989, Private swimming pools (Australian Standard)
Frequently asked questions
When is Water Test Calculator launching?
Approximately 10 days from publication of this page. The app is currently in TestFlight beta and going through Apple App Store and Google Play submission. The official launch date will be announced to the early-access email list before public release.
Is there a free version of Water Test Calculator?
Yes. The free tier includes all core testing functionality, the four calculators, and full app access, ad-supported, with test history limited to the last 7 days. The free tier alone is sufficient for casual pool owners.
Will Water Test Calculator work for my saltwater pool?
Yes. The app has a dedicated saltwater profile that handles salt level tracking, SWG output recommendations, and the higher CYA targets typical of salt pools. Works with all major Australian SWG brands.
How does Water Test Calculator compare to Pool Math?
Pool Math is the long-standing industry standard, free on the web and $5 one-time on mobile. It expects you to enter your CYA reading and look up the correct chlorine target on a chart manually. Water Test Calculator uses the same chemistry foundation but automates the CYA-based targeting, you never have to look up a chart. Full comparison in our app roundup.
Can the app handle indoor pools and spas without CYA?
Yes. Indoor pools don’t need stabiliser (no UV exposure). The app accepts a CYA reading of 0 ppm and applies a different chlorine target accordingly (typically the WHO-recommended 1–3 ppm for indoor pools).
Does Water Test Calculator work without an internet connection?
Yes. The app is offline-first, testing, dosing recommendations, calculators, and history all work without an internet connection. An internet connection is required only for initial app download, optional cloud sync (post v1.1), and in-app subscription management.
Get the launch alert + free checklist
Water Test Calculator launches on iOS and Android in ~10 days. Free with ads. Premium unlocks unlimited test history, smart notifications, and ad-free testing.