Sodium Hypochlorite for Pools Explained

Sodium hypochlorite is an excellent pool disinfectant. Also called liquid pool chlorine or swimming pool shock, this yellow-colored liquid is chemically identical to regular bleach but stronger.

When it comes in contact with water, sodium hypochlorite is an excellent cleaning agent and is a popular choice for most pool owners.

sodium hypochlorite pools

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.

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.

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.

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.

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 proper amounts of cyanuric acid.

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

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.

Wrapping Up

When you are purchasing a disinfectant for your pool, you will most commonly find cal-hypo available. However, if you live in an area where the water is hard and there is a problem with calcium deposits, then it may be much better to use sodium hypochlorite, which will work better to disinfect your pool.

Whichever option you are using, make sure to use it along with a stabilizer like CYA and also, ensure that you are testing all the levels frequently.

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 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!