How Much Chlorine to Add to Pool: Learn the Basics and Avoid Common Mistakes

Chlorine is an essential chemical for keeping your pool water clean and safe. It kills bacteria, algae, and other contaminants that can make your pool cloudy or unhealthy. But how much chlorine do you need to add to your pool? And how often do you need to do it? This guide will help you answer these questions and more.

How Much Chlorine to Add to Your Pool

The amount of chlorine you need to add to your pool depends on several factors, such as:

• The type and concentration of the chlorine product you use
• The volume of your pool
• The current free chlorine level of your pool
• The desired free chlorine level of your pool
• The environmental conditions that affect chlorine demand, such as sunlight, temperature, rainfall, bather load, and organic contamination

To calculate how much chlorine to add to your pool, you can use the following formula or use our calculator for the easiness:

Amount of chlorine (oz) = (Desired free chlorine – Current free chlorine) x Pool volume (gal) x Chlorine multiplier

The chlorine multiplier is a factor that varies depending on the type and concentration of the chlorine product you use. Here are some common values for the chlorine multiplier:

Chlorine product	Concentration	Chlorine multiplier
Trichlor tablets	90%	0.00013
Dichlor granules	56%	0.00017
Cal-hypo granules	65%	0.0001
Lithium granules	35%	0.00029
Liquid chlorine	10%	0.0008
Liquid chlorine	12.5%	0.00064

For example, if you want to raise the free chlorine level of your 10,000-gallon pool from 1 ppm to 3 ppm using liquid chlorine with a concentration of 10%, you need to add:

Amount of chlorine (oz) = (3 – 1) x 10,000 x 0.0008

Amount of chlorine (oz) = 16

This means you need to add 16 ounces of liquid chlorine to your pool.

Alternatively, you can use our handy pool chlorine calculator below to do the math for you. Just enter your pool volume, current free chlorine level desired free chlorine level, and type of chlorine product, and the calculator will tell you how much chlorine to add to your pool.

What is Chlorine and How Does it Work?

Chlorine is a chemical element that has disinfecting properties. When chlorine is added to pool water, it forms hypochlorous acid and hypochlorite ions, which are the active forms of chlorine that kill microorganisms. Chlorine also reacts with organic matter in the water, such as sweat, urine, sunscreen, and cosmetics, to form chloramines, which are byproducts that reduce the effectiveness of chlorine and cause eye irritation and unpleasant odors.

The amount of chlorine in pool water is measured by two parameters: free chlorine and total chlorine.

• Free chlorine is the amount of chlorine that is available for disinfection.
• Total chlorine is the sum of free chlorine and chloramines.
• The difference between total chlorine and free chlorine is called combined chlorine, which indicates the level of chloramines in the water.

The ideal range for free chlorine in pool water is 2-4 parts per million (ppm), according to the South Australian government. This means that for every million parts of water, there should be 2-4 parts of free chlorine. The ideal range for total chlorine is the same as free chlorine, or slightly higher. This means that the combined chlorine level should be less than 0.2 ppm.

To maintain the proper chlorine levels in your pool, you need to test your pool water regularly with a test kit or strips. You also need to add chlorine to your pool periodically, either manually or automatically, depending on the type of chlorine you use.

Types of Chlorine and How to Add Them

There are different types of chlorine products that you can use for your pool, such as tablets, liquid, granular, or salt. Each type has its own advantages and disadvantages, depending on factors such as cost, convenience, availability, and impact on water chemistry. Here is a brief overview of each type:

• Chlorine tablets: These are solid tablets that contain trichloroisocyanuric acid (trichlor) or dichloroisocyanuric acid (dichlor), which are stabilized forms of chlorine that resist degradation by sunlight. Chlorine tablets are easy to use and store, and they provide a steady source of chlorine to your pool. However, they also lower the pH and alkalinity of your water over time, which can cause corrosion and scaling problems. You need to use a tablet feeder or a floating dispenser to add chlorine tablets to your pool.
• Liquid chlorine: This is a liquid solution that contains sodium hypochlorite (bleach), which is an unstabilized form of chlorine that degrades quickly by sunlight. Liquid chlorine is cheap and readily available, and it does not affect the pH or alkalinity of your water significantly. However, it has a short shelf life and it requires frequent dosing and handling. You need to pour liquid chlorine directly into your pool or use a liquid feeder to add it automatically.
• Granular chlorine: This is a powdered or granular product that contains calcium hypochlorite (cal-hypo) or lithium hypochlorite (lithium), which are unstabilized forms of chlorine that degrade slowly by sunlight. Granular chlorine is convenient and versatile, as it can be used for regular chlorination or shock treatment. However, it also raises your water’s pH and calcium hardness over time, which can cause cloudiness and scaling problems. You need to dissolve granular chlorine in a bucket of water before adding it to your pool.
• Salt: This is not a type of chlorine per se, but a way of generating chlorine from salt water using an electrolytic device called a salt chlorinator or salt generator. Salt is cheap and natural, and it provides a constant supply of chlorine to your pool without any handling or storage issues. However, it also requires an initial investment in the salt chlorinator device and regular maintenance of the salt level and cell condition. You need to add salt directly into your pool or use a salt feeder to maintain the salt level.

How Often to Add Chlorine to Your Pool

The frequency of adding chlorine to your pool depends on how fast your pool consumes or loses chlorine. This is influenced by factors such as:

• The type and concentration of the chlorine product you use
• The stabilizer level of your pool
• The environmental conditions that affect chlorine demand, such as sunlight, temperature, rainfall, bather load, and organic contamination

Generally, you should test your pool water at least once a week and add chlorine as needed to maintain the free chlorine level within the ideal range of 2-4 ppm. You should also shock your pool once a week or as needed to eliminate chloramines and other contaminants that reduce the effectiveness of chlorine.

Some types of chlorine products, such as tablets and salt, provide a more consistent and long-lasting source of chlorine than others, such as liquid and granular. However, even if you use these products, you still need to monitor your pool water regularly and adjust the dosage or feeder settings as needed.

Some factors that increase the chlorine demand in your pool are:

• Sunlight: Sunlight degrades unstabilized chlorine rapidly, reducing its disinfecting power. You can protect your chlorine from sunlight by adding a stabilizer or conditioner, such as cyanuric acid (CYA), to your pool. The ideal range for CYA in pool water is 30-50 ppm.
• Temperature: Higher water temperature increases the activity of bacteria and algae, requiring more chlorine to kill them. You can lower your water temperature by using a solar cover or shade cloth, or by adding cool water to your pool.
• Rainfall: Rainwater can dilute your pool water and introduce contaminants that consume chlorine, such as dirt, debris, and organic matter. You can prevent rainfall from affecting your pool by using a solid cover or draining excess water from your pool.
• Bather load: More swimmers in your pool means more organic matter that reacts with chlorine, such as sweat, urine, sunscreen, and cosmetics. You can reduce the impact of bather load by asking swimmers to shower before entering the pool and using a clarifier or flocculant to remove suspended particles from your water.
• Organic contamination: Leaves, grass clippings, insects, and other organic matter that fall into your pool can also consume chlorine and cause cloudiness and algae growth. You can prevent organic contamination by skimming your pool surface regularly and using a leaf net or rake to remove debris from your pool.

Conclusion

Chlorine is an essential chemical for keeping your pool water clean and safe. However, it is not a one-size-fits-all solution. You need to consider various factors when choosing the type and amount of chlorine for your pool. You also need to test your pool water regularly and adjust the dosage as needed.

To make things easier, we have created this guide and calculator to help you figure out how much chlorine to add to your pool. We hope you find them useful and enjoy your swimming experience.