Chlorination chemicals are one of the areas where buyers most often aren't sure which product to specify, because "bleaching powder" and "hypochlorite" get used loosely to mean several different products with quite different available-chlorine content and handling needs.
Stable Bleaching Powder (~30–35% Available Chlorine)
This is calcium hypochlorite-based bleaching powder in its traditional solid form, commonly used for water treatment and general disinfection where a lower, steady chlorine dose is acceptable. It's stable enough for reasonable shelf storage in the right conditions (cool, dry, away from direct sunlight and organic material), but it does leave a calcium-based residue/sludge as it dissolves.
High-Strength Bleaching Powder / Calcium Hypochlorite Granules (65–70% Available Chlorine)
These are the higher-concentration calcium hypochlorite products, most commonly reached for in swimming-pool disinfection and any application where you need a lot of available chlorine in a small storage footprint. Because the available chlorine content is roughly double that of standard bleaching powder, the dose (and the volume you need to store and transport) drops accordingly for the same disinfection target.
See Rensa Calcium Hypochlorite Granules (65–70% Available Chlorine) and Powerit IPC — High Strength Bleaching Powder (Instant Pool Cleaner).
Sodium Hypochlorite Liquid (10–12% Available Chlorine)
Liquid sodium hypochlorite doses precisely through a metering pump and leaves no solid residue, which is why it's the standard choice in many municipal water-treatment and effluent-disinfection plants that already run liquid dosing systems. The trade-off is shelf life: available chlorine in solution degrades faster than in the solid calcium hypochlorite products, especially with heat and light exposure, so stock needs cooler, dark storage and faster turnover.
See Sodium Hypochlorite 10–12%.
Practical Guidance
If you already have liquid dosing infrastructure and can turn over stock reasonably fast, sodium hypochlorite is usually the most convenient. If you need a longer effective shelf life or a smaller storage footprint per unit of available chlorine, one of the higher-strength calcium hypochlorite products is generally the better fit — standard bleaching powder for routine, lower-intensity disinfection, and the 65–70% grade where storage space or dosing volume is tightly constrained.