Spa Switch

Spa Switch is a focused calculator and local log for hot tub owners who manage chlorine by testing their own water and entering their own product assumptions.

Set up one spa profile with tub volume, sanitizer strengths, target free chlorine, refill date, and CYA switch threshold. The free calculator shows today's dichlor or liquid-chlorine dose and the projected CYA added by the current dichlor dose.

Unlock local history to save doses, track accumulated CYA since refill, see when your dichlor-to-liquid switch point is due, save soak-load presets, record pH and alkalinity readings, reset after refills, and export a CSV.

Spa Switch does not diagnose water safety, scan test strips, replace product labels, or recommend ignoring hot tub manufacturer guidance. It uses the values you enter and keeps data on your device.

What's included:
- Current-dose calculator for dichlor and liquid chlorine
- Projected CYA increase for each dichlor dose
- Local dose history with accumulated CYA after unlock
- Switch state for dichlor building, switch due, or switched
- pH and alkalinity trend tracking without correction-dose advice
- Soak-load presets, refill reset, purchase restore, and CSV export