Sodium Hypochlorite for Pools: Unlock Pool Care Secrets

Michael Keenan


Pool Water Chemistry

Do you know about sodium hypochlorite for pools? It’s a powerful sanitizer sometimes used in pools to help get rid of bacteria and other organic matter. Also called liquid pool chlorine, this yellow-colored liquid has a high pH of 13 with around 5% of available chlorine making it ideal for pool owners.

In this article, I’ll dive into the differences between sodium hypochlorite and calcium hypochlorite along with the importance of using Cyanuric Acid or CYA as a chlorine stabilizer. I’ll also explain when sodium hypochlorite is a good choice.

You’ll also learn how to use sodium hypochlorite properly so that your swimming pool is always clean and healthy! Let’s get to it!

sodium hypochlorite pools

Quick Answer:

Sodium hypochlorite is a pool disinfectant that breaks down into hypochlorite and hypochlorous acid when added to water. It’s an effective cleaning agent, but it only has 5% of available chlorine, so it’s not always the best choice for sanitizing. It is often used in hard water areas.

Calcium hypochlorite is also available and contains more chlorine, but can cause calcium deposits in hard water areas. Cyanuric acid is used as a stabilizer with both types of chlorine to make them last longer. Testing levels frequently will help ensure your pool water stays clean and safe.

Need all the details? Then keep reading!

What Is Sodium Hypochlorite?

Sodium hypochlorite is essentially made up of oxygen and chlorine and has a high pH of 13. It is not commonly used in pools by itself because it is unstable. Also, it only has around 5% of available chlorine, which does not make it a very effective sanitizer for your pool.

Not to be confused with sodium bisulfate for pools! I know some of the chemical names sound similar but they usually have different uses. If in doubt check my pool chemistry 101 page – it lists most common pool chemicals and their uses.

How Does Sodium Hypochlorite Work?

When added to water, sodium hypochlorite breaks down into hypochlorite ions and hypochlorous acid, which helps to oxidize, sanitize and kill all the organic matter such as bacteria, algae, spores and human waste such as urine, sweat, oils and spit in your swimming pool.

How to Use Sodium Hypochlorite in Your Pool?

Sodium hypochlorite is a very simple pool sanitizer and because it is already diluted, you can add it to the pool water directly. You can pour the recommended amount of sodium hypochlorite into the pool skimmer and run the pump to distribute it evenly.

beautiful clean pool with a view

Sodium Hypochlorite vs Calcium Hypochlorite

Sodium hypochlorite, as well as calcium hypochlorite, are both disinfectants; however, they are different in terms of their composition. Calcium hypochlorite, commonly called cal-hypo contains calcium, while sodium hypochlorite does not.

Usually, cal-hypo is sold in the solid form or liquid that is pre-diluted and it contains around 65% of chlorine. Since cal-hypo contains calcium, it is not used in pools where the water is very hard and has a high level of calcium and calcium scale.

As we mentioned earlier, sodium hypochlorite does not contain a high level of free chlorine and is also much cheaper to buy. It is a great option for areas having hard water because it does not add calcium. However, if the water that you have is soft water, you will need to add calcium to raise the levels in the water.

Both sodium hypochlorite, as well as calcium hypochlorite, will work as disinfectants and do the job; however, the key difference is the amount of each chemical that you need to add to ensure that the levels are balanced.

hot sun can make sodium hypochlorite degrade

Cyanuric Acid: The Chlorine Stabilizer

Since the chlorine in both sodium hypochlorite and calcium hypochlorite is unstable, it will quickly get eaten up by the UV rays, making it ineffective very quickly. In less than around 20 minutes, half the chlorine will disappear. This is where we make use of CYA or cyanuric acid.

I have a guide explaining more about stabilized and unstabilized chlorine here.

CYA is essentially a chlorine stabilizer that bonds with the ions to prevent the chlorine from breaking down. This essentially means that CYA protects the chlorine from the sun and makes it last longer. Usually, the chlorine tablets you buy from the store already contain the proper amounts of cyanuric acid.

However, if you are using liquid chlorine, then you must read the instructions and make sure to add the correct ammount of CYA because too much can block the effectiveness of the chlorine, causing chlorine lock.

A chlorine lock means that while the pool will test for appropriate amounts of chlorine, it will not sanitize the pool water effectively. Don’t panic though, you can lower the cyanuric acid in your pool using this guide.

The best way to determine this is to test for both the free chlorine, as well as the total chlorine in the pool using a pool testing kit. If the amount of both the free chlorine and total chlorine are out of balance, it means that you probably have a chlorine lock and you will have to shock your pool using a non-chlorine shock.

Common Questions:

When is it a good idea to use sodium hypochlorite in your pool?

If you have hard water (high in calcium) sodium hypochlrite is a good choice of pool disinfectant.

What is the best way to use sodium hypochlorite for swimming pools?

The best way to use sodium hypochlorite for swimming pools is to add it directly to the pool water and circulate it with the pump. It can also be used to brush the walls and floor of the pool as a cleaning agent.

How does sodium hypochlorite help to maintain pool water clarity?

Sodium hypochlorite helps to maintain pool water clarity by killing off any bacteria or contaminants that can cause cloudiness or haziness in the water.

Wrapping Up

When you are chosing a disinfectant for your pool, cal-hypo is usually the most popular. However, if you live in an area where the water is hard and there is a problem with calcium deposits, then it’s much better to use sodium hypochlorite, which will work better to disinfect your pool.

Sodium hypochlorite and calcium hypochlorite are two great disinfectants to choose from for your pool, each with its unique benefits.

Whichever option you are using, it’s important to use a stabilizer like cyanuric acid to ensure that the chlorine stays effective and does its job properly. With these tips in mind, you’ll be able to keep your pool clean and safe!

michael keenan author

Author - Michael Keenan

I'm Michael Keenan the owner and creator of the Outdoor Care Guide. I'm a trained horticulturist with over 30 years of experience in pool care, plant care, and landscape care! Seemed like a good idea to share - I think I can make your life easier and save you some time and money!