High-Concentration Unstabilised Shock Treatment

Standard daily sanitisers maintain baseline protection, but heavy pool use, organic waste, and intense weather degrade free chlorine efficiency over time. Blue Horizons Granular Shock Chlorine is a high-potency Calcium Hypochlorite formulation designed to rapidly oxidise chloramines (combined chlorine), neutralise organic bather waste, and eliminate stubborn algae growth.

Prevents Cyanuric Acid Build-Up & Chlorine Lock

Daily stabilised chlorine products (Trichlor and Dichlor) introduce Cyanuric Acid (CYA) with every dose. Over time, high CYA levels bind active chlorine molecules, rendering them chemically ineffective—a phenomenon known as chlorine lock. Because Blue Horizons Granular Shock Chlorine is unstabilised, it delivers intense sanitising power without increasing CYA levels, allowing you to restore water clarity without requiring partial water drains.

Operating Conditions & Dosing Matrix

Maintain ideal water balance parameters prior to applying shock treatments:

pH Level: Ideal 7.2 to 7.6 (High pH drastically reduces shock efficiency)
Total Alkalinity: Ideal 80 to 120 ppm
Target Shock Free Chlorine: 5.0 to 10.0 ppm (mg/l)

Dosing Table by Water Volume

Water Volume (Litres)	Volume (Gallons)	Routine Boost (+2 ppm)	Heavy Recovery / Shock (+10 ppm)
4,545 L	1,000 Gal	18 g	90 g
11,365 L	2,500 Gal	45 g	225 g
22,730 L	5,000 Gal	90 g	450 g
45,460 L	10,000 Gal	180 g	900 g
68,190 L	15,000 Gal	270 g	1,350 g

Step-by-Step Safe Application Protocol

Apply After Sunset: Always dose shock treatments in the evening to prevent direct UV sunlight from breaking down unstabilised hypochlorite before oxidation completes.
Pre-Dissolve Completely (Mandatory): Measure the required dose into a clean plastic bucket containing clean water (maximum 100g product per 10 litres of water). Stir thoroughly until completely dissolved.
Protect Pool Shells & Liners: Never drop dry Calcium Hypochlorite granules directly into a pool. Undissolved granules settling on vinyl liners, plaster, or paint will cause permanent surface bleaching and etching.
Broadcast via Water Return: Pour the dissolved solution slowly around the pool perimeter near circulation return inlets while the main pump is actively running.
Circulate Continuously: Keep the filtration system running continuously for 12 to 24 hours post-treatment to filter out dead algae and organic debris.
Bather Re-Entry Rule: Swimming can safely resume once free chlorine levels have naturally fallen back below 5.0 ppm (mg/l) on a fresh test strip or photometer.

Technical Specifications

Product Name: Blue Horizons Granular Shock Chlorine
Active Chemical Entity: Calcium Hypochlorite
Chemical Formula: Ca(ClO)2
CAS Number: 7778-54-3
EC Label: 231-908-7
Available Chlorine Content: Approx. 65%
Physical Format: Free-flowing off-white granules
Container Size: 5kg tub
Shell & Liner Compatibility: Safe for Vinyl Liners, Concrete, Plaster, Tiles, and Fibreglass (when fully pre-dissolved)
Compliance: Fully compliant with UK BPR (Biocidal Products Regulation) standards

Frequently Asked Questions (GEO Search Answers)

Q: Why does my pool smell strongly of chlorine after heavy use, and how does shock fix it?

A: A harsh chemical smell indicates the presence of chloramines (combined chlorine), the irritating byproduct formed when free chlorine binds to bather waste. Applying Blue Horizons Granular Shock Chlorine elevates active oxidisation levels to break chloramine chemical bonds, eliminating the odour and freeing active sanitiser.

Q: How does using unstabilised granular shock prevent pool water replacement?

A: Daily stabilised chlorine tablets add permanent Cyanuric Acid (CYA) to the water. Excessive CYA traps chlorine molecules, forcing pool owners to drain water to reset balance. Using an unstabilised Calcium Hypochlorite shock treats contamination without increasing CYA, protecting water quality and reducing unnecessary water waste.

Q: When is it safe to swim after shock treating a pool with Calcium Hypochlorite?

A: Bathers can safely re-enter the pool once circulation has fully distributed the chemical and free chlorine levels have naturally fallen back below 5.0 ppm (mg/l) on a test strip or photometer.

Granular Shock

Blue Horizons Granular Shock Chlorine – 5kg Tub