Pool Chlorine Shock Granules - Rapid Dissolve

Fast-acting unstabilised chlorine shock granules for pools. Hits 10 ppm in minutes to break chloramines, kill algae and clear cloudy water without adding stabiliser.

• Lifts free chlorine to 10 ppm in minutes for a standard shock.
• Breaks chloramines and restores breakpoint chlorination.
• Kills early algae blooms before they bind to surfaces.
• Clears organic load after thunderstorms or heavy bather use.
• Adds no cyanuric acid, ideal for high-CYA water.

Sizes and prices

• 5kg: £36.00
• 10kg: £70.75
• 25kg: £175.00

When you need it

• Combined chlorine reads above 0.3 ppm.
• Water is cloudy or smells strongly of chlorine.
• Algae is forming in corners or on steps.
• Bather load just spiked through a hot weekend.
• Free chlorine has tested zero unexpectedly.

How to use

1. Test pH and bring into 7.2-7.6 band before shocking.
2. Brush all walls, steps and corners with a pool brush.
3. Pre-dissolve dose in a 10 L bucket of pool water.
4. Pour clear solution evenly across the deep end with circulation running.
5. Run filtration continuously for 12-24 hours after shocking.
6. Test free chlorine; do not bathe until below 5 ppm.

Dosing guide

Use 75 g per m³ for a standard 5 ppm shock or 150 g per m³ for a 10 ppm algae shock. pH will rise; test and rebalance with pH Minus afterwards.

• For 20 m³, add 1.5 kg to reach 5 ppm shock.
• For 40 m³, add 3.0 kg to reach 5 ppm shock.
• For 20 m³, add 3.0 kg to reach 10 ppm algae shock.
• For 40 m³, add 6.0 kg to reach 10 ppm algae shock.
• For 60 m³, add 18 kg to reach 20 ppm black-spot shock.

How it works

Calcium hypochlorite granules at 65% available chlorine, unstabilised; the same active as Cal-Hypo Granules but pre-portioned in 1 kg sachets for clean shocking.

Hypochlorous acid (HOCl) released from cal-hypo oxidises chloramines, ammonia and organic load. Without cyanuric acid present, every gram of dosed chlorine is bioavailable and kills on contact.

Stabilised chlorine cannot break the chloramine ceiling once cyanuric acid is over 50 ppm. An unstabilised shock is the only way to restore breakpoint and clear water.

Frequently asked questions

How often should I shock?

Once a week in summer, every two weeks in shoulder seasons, immediately after thunderstorms or heavy bather use.

Standard shock or algae shock?

Standard 5 ppm for routine; 10 ppm for visible algae; 20 ppm for black-spot or yellow algae.

Will it raise my CYA?

No. This is unstabilised cal-hypo; no cyanuric acid is added.

How is it different from cal-hypo granules?

Same active ingredient, but supplied in 1 kg pre-measured shock sachets for tidy weekly dosing.

Pack sizes?

5 kg and 10 kg cartons of 1 kg sachets.

Can I use it in a vinyl pool?

Yes if you pre-dissolve in a bucket; never broadcast dry granules onto a vinyl liner.

What is the active ingredient?

Calcium hypochlorite at 65% available chlorine, unstabilised.

Why no stabiliser?

Stabilised shocks cannot break chloramines once CYA is over 50 ppm; you need bioavailable chlorine to oxidise.

Algae won't clear?

Increase shock to 20 ppm; brush walls; vacuum dead algae to waste, not back through filter.

pH spiked?

Dose pH Minus to bring pH back to 7.2-7.6 within 4 hours.

Chlorine shock vs MPS shock?

Chlorine kills algae and bacteria; MPS oxidises organic load only. Use chlorine for algae, MPS for routine clarity.

Chlorine shock vs rapid shock tablets?

Granules dissolve in minutes for whole-pool shocks; tablets target individual problem zones via skimmer.