Stabilised Chlorine Granules SDIC

Stabilised chlorine granules that dissolve fast for instant top-ups and pH-neutral shocks. SDIC adds 1 ppm of free chlorine per 1.4 g per 1000 L without raising pH.

• Adds 1 ppm of free chlorine per 1.4 g per 1000 L.
• Dissolves fully in 60 seconds, with no residue.
• pH-neutral, so balance is preserved after dosing.
• Stabilised against UV burn-off with built-in cyanuric acid.
• Suitable for daily top-ups, weekly shocks and post-fill chlorination.

Sizes and prices

• 1kg: £9.95
• 2.5kg: £17.62
• 5kg: £30.41
• 10kg: £55.98
• 20kg: £107.14
• 25kg: £132.71

When you need it

• Free chlorine has dropped below 1 ppm.
• You need an instant top-up after a heavy soak.
• It is time for a weekly shock and you want pH stability.
• You have just refilled and need to chlorinate the new fill.
• You want to avoid the pH drift that comes with TCCA tablets.

How to use

1. Test free chlorine, pH and total alkalinity.
2. Confirm pH is 7.2-7.6 and alkalinity 80-120 ppm.
3. Pre-dissolve the dose in 5 L of warm tub water and stir.
4. Switch the pump to circulation and pour the solution slowly across the surface.
5. Run circulation for 30-60 minutes; retest free chlorine.
6. Wait until free chlorine drops below 5 ppm before bathing.

Dosing guide

Standard dose adds 1 ppm. For a 5 ppm shock multiply by 5. For a fresh fill establishment, dose 5-10 ppm and run circulation for 4 hours.

• For 1,000 L, add 1.4 g to reach +1 ppm top-up.
• For 1,500 L, add 4.2 g to reach +2 ppm top-up.
• For 2,000 L, add 14 g to reach +5 ppm shock.
• For 5,000 L (swim spa), add 35 g to reach +5 ppm shock.
• For 10,000 L (pool), add 70 g to reach +5 ppm shock.

How it works

Sodium dichloroisocyanurate dihydrate (SDIC), supplied as fast-dissolving granules with at least 56% available chlorine and built-in cyanuric acid stabilisation.

SDIC dissolves to release hypochlorous acid (the active sanitiser) and cyanuric acid (the stabiliser). Unlike TCCA, the granules are pH-neutral, so balance is preserved while sanitiser is added or shocked. The cyanuric acid binds reversibly to chlorine and protects it from UV destruction.

Daily chlorine top-ups must not destabilise pH. SDIC is the standard pool-grade granule for that job. Its fast dissolution makes it ideal for shocks too, where speed and pH stability both matter.

Frequently asked questions

How much SDIC raises chlorine by 1 ppm?

1.4 g per 1000 L raises free chlorine by 1 ppm.

Is SDIC pH-neutral?

Yes. SDIC is the pH-neutral chlorine donor used worldwide for daily dosing.

How long until I can bathe?

Wait until free chlorine drops below 5 ppm; usually 60 minutes after a top-up.

How long does a 1 kg pack last?

Around 6-12 months of weekly maintenance for a 1500 L hot tub.

Will SDIC work in salt systems?

Yes. The granules supplement salt chlorination during heavy bather load.

Can I shock with SDIC?

Yes. Dose 5 ppm of free chlorine for a routine shock or 10 ppm for a heavy shock.

What is the active ingredient?

Sodium dichloroisocyanurate dihydrate (SDIC) at >= 56% available chlorine.

Why does SDIC not affect pH?

The dichloro-cyanurate ion is balanced between acidic and basic groups, so pH stays in band as the granules dissolve.

Does SDIC raise stabiliser?

Yes. Each 10 ppm of free chlorine added by SDIC adds approximately 6 ppm of cyanuric acid.

Chlorine not climbing?

High combined chlorine; shock at 10 ppm and run circulation for 4 hours.

Cloudy water after dosing?

Dose was added neat or pH out of band; rebalance and clean filter.

CYA too high?

Switch to calcium hypochlorite for shocks; refresh part of the water if CYA above 80 ppm.

SDIC vs TCCA tablets?

SDIC is fast-dissolving, pH-neutral granules for daily and shock dosing. TCCA is slow-release, acidic tablets for low-effort dispensing.

SDIC vs calcium hypochlorite?

SDIC is stabilised and gentle on pH. Calcium hypochlorite is unstabilised, faster acting, and raises pH; better for indoor pools and CYA-saturated water.