2 Litres

For a hot tub up to 1 m³ at the standard 30 ml weekly dose, one bottle covers about 33 weekly applications — roughly eight months of care after the start phase.

Yes. WhirlBiotic is compatible with reduced amounts of chlorine or bromine. Very high spikes can temporarily suppress the cultures — once they subside, the microbiome rebuilds itself. Where chlorine or bromine is legally required, WhirlBiotic does not replace it.

Start phase: 30 ml daily for three consecutive days. After that, dose once per week — the weekly amount depends on your water volume (30 ml up to 1 m³, 50 ml up to 2 m³, 100 ml up to 4 m³, 150 ml up to 6 m³). The full dosing table is on the How it works page.