Is Calcium Hypochlorite the same as bleach?

The short answer is no.

Calcium hypochlorite and bleaching water are indeed very similar. They both are unstabilized chlorine and both release hypochlorous acid in the water for disinfection.

Although, their detailed properties result in different application characteristics and dosing methods. Let’s compare them one by one as follows:

1. Forms and available chlorine content

Calcium hypochlorite is sold in granular or tablet form and its available chlorine content is between 65% to 70%.

Bleaching water is sold in solution form. Its available chlorine content is between 5% to 12% and its pH is about 13.

This means that the bleaching water requires more storage space and more manpower to use.

2. Dosing methods

Calcium hypochlorite granules should be dissolved in water first. Because calcium hypochlorite always contains more than 2% of undissolved matter, the solution is very turbid and a pool maintainer must let the solution settle and then use the supernatant. For calcium hypochlorite tablets, just put them in the special feeder.

Bleach water is a solution that a pool maintainer can add directly to a swimming pool.

3. Calcium hardness

Calcium hypochlorite increases the calcium hardness of pool water and 1 ppm of calcium hypochlorite lead to 1 ppm of calcium hardness. This is beneficial for flocculation, but is a trouble for water with higher hardness (higher than 800 to 1000 ppm) — may cause scaling.

Bleaching water never causes increase of calcium hardness.

4. pH Increase

Bleaching water causes a greater pH rise than calcium hypochlorite.

5. Shelf Life

Calcium hypochlorite loses 6% or more of available chlorine per year, so its shelf life is one to two years.

Bleaching water loses available chlorine at a much higher rate. The higher the concentration, the faster the loss. For a 6% bleaching water, its available chlorine content will decrease to 3.3% after one year (45% loss); while a 9% bleaching water will become a 3.6% bleaching water (60% loss). It can even be said that the effective chlorine concentration of the bleach you buy is a mystery. Therefore, it is difficult to determine its dosage accurately and also control the effective chlorine level in the pool water accurately.

Seemingly, bleaching water is cost-saving, but users will find that calcium hypochlorite is more favorable when considering the validity period.

6. Storage and Safety

The two chemicals should be stored in a tightly closed container and placed in a cool, dry, well-ventilated area away from incompatible substances, especially acids.

Calcium hypochlorite is known to be highly dangerous. It will smoke and catch fire when mixed with grease, glycerin or other flammable substances. When heated to 70°C by fire or sunshine, it may decompose quickly and cause danger. So a user must be extra careful when storing and using it.

However, bleaching water is safer for storage. It almost never causes fire or explosion under normal application conditions. Even if it comes into contact with acid, it releases chlorine gas more slowly and less.

Short-term contact with calcium hypochlorite by dry hands does not cause irritation, but short-term contact with bleaching water will also cause irritation. However, it is recommended to wear rubber gloves, masks, and goggles when using these two chemicals.