Chemistry apps
1. Spa Calc
Best for: any hot tub, inflatables included.
The first screen says whether it's ready to soak, from your sanitizer and pH. Doses come in teaspoons down to an eighth, or grams, for any brand at the strength on its label. It handles bromine, chlorine (dichlor then bleach, with a stabilizer tracker), MPS, salt, and ozone, UV and mineral systems. "I just soaked" gives a top-up after each soak, and a drain countdown is worked out from the tub's size and use. Free for one tub with every feature, no account and no ads. Plus covers up to 10 tubs for rental hosts; Pro is unlimited for service techs.
Why it isn't perfect: it's new (on the App Store at launch), iPhone only, English at launch, and it doesn't read strips from a photo or control the tub.
2. FROG Water Care
Best for: owners using a FROG sanitizing system.
Reads FROG and FROG @ease strips, gives step-by-step recommendations and dosage guidance for pool, hot tub or swim spa, and keeps your history. Rated 4.5 from 4.9K. It requires sign-in, and its guidance is written around FROG systems. Compare with Spa Calc.
3. HTH Pools App
Best for: HTH spa strip users who also have a pool.
Free and highly rated (4.7 from 4.1K across pool and spa use), with spa strip matching and newly announced spa water testing. Recommendations are HTH products, and saving history uses a myHTH account. Compare with Spa Calc.
4. Pool Math by TroubleFreePool
Best for: pool and spa owners on the TroubleFreePool method.
A pool calculator that holds spa configurations on Premium ($7.99 a year). A 2022 reviewer asked for more spa-specific options and for MPS. Compare with Spa Calc.
Controller apps (use alongside a chemistry app)
1. Bestway Connect (SmartSpa)
Best for: Wi-Fi Lay-Z-Spa models with a QR code on the pump panel.
Heating, filtration, timers and massage bubbles from your phone. Rated 4.6 from 1K. Its listing doesn't describe water chemistry. Compare with Spa Calc.
2. INTEX Link
Best for: Intex PureSpa models with the Wi-Fi icon.
Heater, idle temperature, maintenance schedules and, on select models, scheduled chlorination with filtration, over Bluetooth or 2.4 GHz Wi-Fi. Rated 2.2 from 17; one reviewer reports having to re-add the spa after every device reset. Compare with Spa Calc.
3. Bestway Smart Hub
Best for: the AirJet Plus spa and the Smart Touch Wi-Fi pump.
Remote heater, timer and massage control. Rated 1.7 from 260, with reviewers reporting setup and pairing trouble. Bestway's listing sends owners of QR-code pumps to Bestway Connect (SmartSpa) instead. Compare with Spa Calc.