Which chlorine level is best for a hot tub?

Keep free chlorine at 3 to 5 ppm, checking with strips or a photometer at least two or three times weekly. Heated spa water uses chlorine faster than a swimming pool does, so increase testing when bathing demand is high.

Which bromine level is best for a hot tub?

Maintain total bromine at 4 to 6 ppm. For hot tubs, bromine offers steadier performance because heated water and a broader pH range affect it less than chlorine.

Why is 7.2 to 7.6 the required hot tub pH?

This range supports efficient sanitiser action while keeping water comfortable and non-corrosive. Over 7.6, chlorine becomes less effective and scale develops; under 7.2, water may irritate bathers and attack equipment.

When is it safe to bathe after adding chemicals?

For routine non-chlorine shock, circulate first and retest; bathe only once the sanitiser is within range. Following chlorine shock, free chlorine must return below 5 ppm. Use the waiting instructions printed on that product's label.

UK Hot Tub Water Chemistry: The Reference

One citeable resource brings together wait rules, target ranges and comparisons drawn from Zagosa Spa & Pool labels and Zagosa Industrial guidance.

Free chlorine: 3 to 5 ppm - Provides sanitising action in heated spa water; reliable bacterial control cannot be expected below 3 ppm.
Total bromine: 4 to 6 ppm - This is the corresponding bromine band; in heated water, bromine remains active across more pH conditions.
pH: 7.2 to 7.6 - Within this band, chlorine performs well while water remains comfortable for bathers and gentler on equipment.
Total alkalinity: 80 to 120 ppm - It resists sudden pH movement; when alkalinity is outside range, a stable pH reading is difficult to maintain.
Calcium hardness: 150 to 250 ppm - Low hardness can corrode equipment, whereas excessive hardness deposits scale over heaters, plumbing and the shell.