Chlorine tablets vs liquid chlorine: which to choose for your pool
The decisive difference between tablets and liquid chlorine is not convenience, it is the stabiliser: tablets add it, liquid does not. That is what should guide your choice.
In short
Tablets (slow chlorine) are convenient and self-dispensing, but most are stabilised: they raise the stabiliser, which builds up and eventually locks the chlorine. Liquid chlorine adds no stabiliser and allows precise dosing, but must be added regularly. Simple rule: tablets when the stabiliser is low, liquid when it is already high.
Tablets: convenience, but stabiliser build-up
Tablets go in the skimmers or a dispenser and release chlorine slowly, with no daily handling. The downside: most tablets are stabilised, so each one adds stabiliser. Over the season the level rises, and above about 70 mg/L chlorine becomes ineffective even when well dosed.
Liquid chlorine: precise dosing, no stabiliser
Liquid chlorine acts fast and adds no stabiliser: it is the right option when the stabiliser is already high, or to keep control of the level. In return, it is consumed faster in the sun (less protected) and needs regular additions, plus careful storage and handling.
What to do, step by step
Measure your stabiliser
This is the deciding factor. Below 30 mg/L, stabilised tablets make sense; above 70, avoid them.
Low stabiliser: tablets are fine
Tablets bring convenience and some useful stabiliser to protect chlorine from the sun.
High stabiliser: liquid chlorine
Switch to liquid (unstabilised) chlorine so as not to worsen the build-up, while you renew part of the water.
Either way: keep the pH in range
At a correct pH (7.0–7.4), chlorine — tablets or liquid — stays effective.
Frequently asked questions
Is liquid chlorine stronger than tablets?
It acts faster but is consumed faster in the sun, because it is unstabilised. Tablets, slower, last longer but build up stabiliser.
Can I alternate tablets and liquid chlorine?
Yes, and it is good practice: tablets for convenience, liquid to stop the stabiliser rising too much. Just monitor the stabiliser level.
Why does my water turn green despite tablets?
Often because the stabiliser added by tablets is too high and locks the chlorine. Test it: above 70 mg/L, renew part of the water and switch to unstabilised chlorine.