Safe use of chlorine to disinfect water in swimming pools and spas

The water in pools and spas can be contaminated by microorganisms such as bacteria, viruses and parasites. These microorganisms can cause health problems. It is therefore necessary to disinfect water in order to prevent it from becoming contaminated. Commonly used chemical products often contain chlorine, a known disinfectant. These products are called “chlorinating agents”.

Chlorinating agents are available in two forms:

• Dry products, which come in granular or tablet form
• Liquid products, such as “liquid chlorine” (bleach, for example)

There are two main types of chlorinating agents:

• Inorganic, such as bleach (sodium hypochlorite) or chlorine granules (calcium hypochlorite)
• Organic (containing carbon), such as chlorine tablets (trichloroisocyanuric acid)

Inorganic and organic products should not be mixed due to a risk of explosion.

In order to protect the health of bathers, you must analyze the water in your pool or spa daily to verify how much chlorine it contains. You can buy a kit for analyzing water at stores that specialize in the sale, installation and maintenance of pools or at hardware stores.

The concentration of chlorine in water is measured in milligrams per litre or mg/L. Make sure that the chlorine concentration in the water of your pool or spa is within the limits established by the Regulation respecting water quality in swimming pools and other artificial pools  of the Ministère de l’Environnement et de la Lutte contre les changements climatiques, which are:

• Swimming pools, including inflatable pools: between 0.8 and 3 mg/L
  If you have an inflatable pool, read the manufacturer’s instructions carefully. They will tell you how much chlorine to add to pool water in order to get a concentration of between 0.8 and 3 mg/L
• Spas: between 2 and 3 mg/L.
  Spa water is warmer than pool water, which promotes the growth of microorganisms. A greater quantity of chlorine is therefore necessary to disinfect spa water

Chlorinating agents are dangerous. You must use them carefully and store them correctly to avoid certain risks:

• Risk of fire or explosion
• Risk of chlorine gas fumes
• Health hazards associated with toxic or corrosive products

Chlorinating agents can cause fires or explosions if they come into contact with flammable materials such as gasoline, paint or solvents.

It is also very important to avoid mixing inorganic and organic chlorinating agents together as such mixtures can cause explosions. 

Mixing chlorinating agents with certain other products may result in the release of chlorine gas, which is highly toxic.

For example, avoid mixing out of the water a chlorinating agent, such as bleach (sodium hypochlorite), with an acidic product used to adjust the acidity (pH) of water, such as muriatic acid (hydrochloric acid).

Some chlorinating agents can be toxic or corrosive. Generally, corrosive products can cause minor to severe lesions as soon as they come into contact with:

• Skin
• Eyes
• Respiratory tract
• Digestive tract

You may experience the following if you inhale fumes from chlorinating agents:

• Irritation of the nose and throat
• Severe respiratory problems, especially in the case of chlorine poisoning

To protect your health and ensure your safety, take some precautions when handling or storing chlorinating agents.

Handle products safely

• Before using chlorinating agents, follow the instructions on the label. Read the first-aid instructions beforehand in case of poisoning
• Wear protective gear and clothing (such as gloves, glasses and shoes)
• Handle the products outdoors or in a well-ventilated area
• Keep children away from the area where the products are being used
• Use a clean and dry measuring cup to measure or pour products. Use a different cup for each product
• To prevent the risk of a fire or an explosion, avoid mixing 2 or more different chemical products
• Always pour the chlorinating agent into water, never the other way round (water into the chlorinating agent)
• Wash your hands thoroughly after handling products

Store products safely

• Read the label to find out how to store the product properly
• Store products in a cool, dry, well-ventilated place that is not exposed to sunlight. If the temperature rises, toxic fumes can accumulate in the product containers and escape into the air when opened
• Never store chlorinating agents, such as bleach, near acidic products, such as those used to lower the pH of water. If they come into contact with each other, these products can release chlorine gas, which is highly toxic
• Keep chemical products far away from:
  • Heat sources
  • Flames
  • Gasoline
  • Fertilizer
  • Pesticides
  • Oil or grease
  • Paint
  • Cleaning products
  • Turpentine
  • Other flammable products 
• Store containers of liquid chlorinating agents under those of powder or solid products, never the other way around. This will prevent the products from coming into contact with each other if a liquid spills from its container
• Get rid of leftover products at an authorized household-hazardous-waste collection centre. To find a centre near you, contact your municipality

In case of fire

• Do not use a dry chemical fire extinguisher. Douse the fire with lots of water
  and call 9-1-1

In case of explosion

• If an explosion occurs, call 9-1-1

In case of poisoning or prolonged contact of the skin or eyes with a chlorinating agent

• Move away from the source of contamination. Immediately remove contaminated clothes and shoes  
• Spray the contaminated area lightly with warm water for at least 15 to 20 minutes. Spray longer if it is a corrosive chemical product
• Dial 9-1-1 or call the Centre antipoison (poison control centre) at 1-800-463-5060