How much liquid chlorine should I put in my pool?

Updated February 21, 2017

You've heard that you should add chlorine to your swimming pool water, but that's all you've heard about chlorine. Now the question you're asking yourself is, "How much liquid chlorine should I put in my pool?" It is necessary to add chlorine to pool water because chlorine kills algae and bacteria, and it destroys any organic matter that might be in the water. How much chlorine you should put in the pool is determined by how much water is in the pool and the level of chlorine already in the pool.

Test the chlorine level

You must purchase a pool test kit to check the chlorine level. These are sold as a single test set for chlorine only or as a duplex test kit, which can test for pH as well as chlorine. The chlorine test will indicate the chlorine concentration in the pool water by showing a simple pool water colour change which can be compared to standardised colour codes. This test should be conducted daily to check for residual chlorine .

Amount of chlorine required

The amount of chlorine required is determined by the type of chlorine you are using. For calcium hypochlorite granular, use around 3 g of chlorine per 1,000 litres (or half ounce per 1,000 gallons) of water. For calcium hypochlorite tablets the correct amount can be determined based on the weight of each tablet. For sodium hypochlorite 15% solution, use 10 ml of chlorine per 1,000 litres (or 1.5 fluid ounces chlorine per 1,000 gallons) of water. For sodium or potassium dichloroisocyanurate, use a 1.6 g per 1,000 litres (a quarter ounce per 1,000 gallons) of water. These guidelines provide chlorine dosages that will be effective for normal treatment. Always follow the manufacturer's directions for individual products. During the initial treatment, you should double dosages for the first three days.

Adding the chlorine

Liquid chlorine is produced in concentrated form just for using in pools. It contains about 10 to 16 per cent pure chlorine. Avoid getting the solution on your clothes and skin. The chlorine can be poured directly into the swimming pool, but it is necessary to distribute it over as much of the pool as possible. Pour it into the water slowly as you circle around the pool. Place the container very close to the water to avoid splashing yourself. The best time to chlorinate is after the sun has set in the evening, and you are finished swimming for the day. Sunlight and high temperatures can cause the chlorine to dissipate quickly.

Shock treatment

If your swimming pool continues to show low levels of chlorine, it will allow various organisms the opportunity to develop that may be more resistant to normal chlorine concentrations. Then you should engage in shock treatment, a treatment intended to control the organisms and burn out other organic matter that has accumulated. Shock treatment requires you to place five to ten times the regular dosage of chlorine once every two weeks.

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