4 min read · TopTubs Lincolnshire Ltd
Shocking your hot tub is one of those maintenance tasks that sounds dramatic but is actually simple routine care. Done weekly, it keeps your water genuinely clean rather than just chemically suppressed. This guide explains exactly what it does and how to do it properly.
Your sanitiser (chlorine or bromine) kills bacteria — but over time it gets used up fighting organic contaminants: body oils, sweat, sunscreen, cosmetics and dead skin cells. These contaminants combine with chlorine to form chloramines — the compound responsible for that "swimming pool" smell and eye irritation. Shock treatment oxidises and destroys these combined compounds, freeing up your sanitiser to work properly again.
That chlorine smell doesn't mean you have too much chlorine. It means you have too little free chlorine — and too many chloramines. Shock the tub.
Chlorine shock (calcium hypochlorite or dichlor): A strong oxidiser that also boosts chlorine levels significantly. Use for a heavy clean after a party or if the water has gone very cloudy. Wait 8–24 hours before bathing.
Non-chlorine shock (potassium monopersulphate / MPS): Oxidises contaminants without raising chlorine levels. Better for weekly routine use — you can typically bathe 30 minutes after dosing. Safe for use with both chlorine and bromine systems.
For weekly maintenance, non-chlorine shock is the right choice. Use chlorine shock only for heavy oxidation jobs.
If shocking doesn't clear the water within 24 hours, it may be time for a drain and refill.