Spa Calcium Hypochlorite Granules

A fast unstabilised chlorine shock for pools and indoor spas. 65% calcium hypochlorite granules deliver a 5-10 ppm chlorine kick in minutes, with no cyanuric acid build-up.

• Adds 1 ppm of free chlorine per 1.5 g per 1000 L.
• Burns through algae blooms and high combined chlorine.
• Adds calcium hardness (~7 ppm per 5 g per 1000 L).
• Carries no cyanuric acid, so it suits indoor pools.
• Suits periodic super-chlorination of spas with high CYA.

Sizes and prices

Available in 1kg, 2.5kg, 5kg, 10kg, 20kg, 25kg.

• 1kg: £13.25
• 2.5kg: £23.85
• 5kg: £41.52
• 10kg: £76.86
• 20kg: £147.53
• 25kg: £182.87

How to use

1. Test free chlorine, pH, alkalinity and CYA.
2. Confirm pH is 7.2-7.6 before shocking.
3. Dissolve the dose first in 10 L of warm water using a clean plastic bucket.
4. Set the pump to circulation and pour the solution slowly across the surface.
5. Circulate for at least 4 hours; do not bathe.
6. Wait for free chlorine to drop below 5 ppm before bathing.

Frequently asked questions

How much do I add for a 5 ppm shock?

Around 7.5 g per 1000 L of water, pre-dissolved in 10 L of warm water before adding.

Does it raise pH?

Yes. Each 1 ppm of chlorine added with calcium hypochlorite lifts pH by about 0.05 units.

How long before I can bathe?

Wait for free chlorine to fall below 5 ppm, usually 4-12 hours after a shock.

How long does a 5 kg pack last?

Around 30-50 standard pool shocks for a 30 m3 pool.

Is it safe for vinyl liners?

Yes, once fully pre-dissolved. Never scatter dry granules onto a vinyl liner.

Can I use it in a hot tub?

Only as a periodic CYA reset shock. Day-to-day dosing in hot tubs should use SDIC, TCCA tablets or bromine.

What is the active ingredient?

Calcium hypochlorite (Ca(OCl)2) at >= 65% available chlorine.

Why does it raise calcium?

Each calcium hypochlorite molecule releases one calcium ion alongside two chlorines.

Why use unstabilised chlorine?

Stabilised chlorine builds CYA. Calcium hypochlorite delivers chlorine without CYA, which suits indoor pools and CYA-saturated water.

Cloudy water after shock?

Granules went in dry or pH is out of band. Filter for 24 hours and dose clarifier.

pH spike after shock?

Dose pH minus per the table to bring pH back to 7.4.

Algae returning?

Clean the filter overnight, vacuum dead algae, dose clarifier.

Calcium hypo or SDIC?

Calcium hypochlorite is unstabilised, alkaline and adds calcium. SDIC is stabilised, pH-neutral and adds CYA.

Calcium hypo or liquid bleach?

Both are unstabilised chlorine. Granules are easier to store and dose; liquid bleach is faster to dose but harder to handle.