Granular Chlorine

Granular Chlorine

Granular chlorine is of three types, which are classified according to the concentration of chlorine in the product. While calcium hypochlorite and lithium hypochlorite are commonly used for pools; spa treatment is better done with dichlor.
Gardenerdy Staff
When it comes to swimming pool care and maintenance, chlorine is a multipurpose ingredient. It kills unwanted pool algae and microbes, and maintains the nutrient balance in pool water by nullifying nitrogen compounds. No wonder, its use for disinfection is highly appreciated in medicinal facilities too. Despite the name, granular chlorine is not necessarily sold as granules, but it is also available in powder form.

What is Granular Chlorine?

The name itself denotes that it is a dry, granular form of chlorine. Another dry version of is found in the form of tablets. Both are safe and effective for disinfecting pools, but the choice is up to the pool owner. When applied for treating swimming pool algae and other microbial contamination, the chlorine penetrates the cell walls of organisms and kills them by oxidization. However, it is to be borne in mind that any form of it, including the liquid and dry forms are hazardous for health.

Depending on the percentage content of chlorine in the final products, there are three kinds. They are calcium hypochlorite (65 percent), dichlor (62 percent), and lithium hypochlorite (35 percent). Each of these has its own advantages and limitations in sanitizing pools. Of these types, calcium hypochlorite is the most popularly used product.

In comparison to other products, calcium hypochlorite (or Cal-hypo) is less expensive, easy to dissolve, and more effective in killing pool microbes. However, it is not recommended for sanitizing hot tubs. Being a calcium containing compound, it tends to leave unwanted scale ring in hot water tub, and also in parts of the spa heater. A better type for spas is dichlor. Sold in packages of various sizes, it is excellent for shock treatment in spas. Lithium hypochlorite, on the other hand, is a highly stable product, which application is similar to calcium hypochlorite.

Use in Pools

At the first mention of granular chlorine, swimming pool chemicals are the first things that come up in everyone's mind. However, with so many products in the market, purchasing one for using in swimming pool chemical treatment methods can be quite confusing for pool owners. You can use dichlor for regular cleaning or shock treatment. Though lithium hypochlorite is less toxic and readily soluble, you will require high amount of this product to get the desired results.

It is suggested that specific care be taken while using calcium hypochlorite in pools. Even the granular form produces some amount of dust, which is harmful for health and may cause an episode of allergy. So, proper precaution should be taken while handling it to avoid accidental inhalation. Also, you need to determine sufficient amounts of this dry chlorine according to the quantity of pool water. Then, dissolve it completely in water, and use the solution form for pool water treatment.


Using chlorine is indeed the safest and cheapest way of cleaning pool water. To cut down costs of pool water disinfection or occasional spa shock treatment, you can store leftover granular chlorine in a proper way for use in the next session. Keep granules in the original container, and seal the lid tightly. Remember that calcium hypochlorite is a caustic compound, and can poison pets when ingested. For increasing shelf life, you can store the container in a cool and dry place, away from high temperature and direct sunlight exposure.

If at all, you want to store the product for a longer period, go for the dichlor, it has a longer shelf life. In case you are doubtful about the type of product for your swimming pool, first learn granular vs. liquid chlorine, and their applications. While the former requires a preparatory step of dissolving in water, the latter is a highly alkaline solution (pH 13) that can be used directly in pool water. However, it needs to be purchased in bulk (may not be affordable), and requires further acid treatment for balancing pH of pool water.