Chlorine Shock vs Non-Chlorine Shock: What’s The Difference

If you are new to swimming pool maintenance, you may be wondering about the best way to shock your swimming pool when the combined chlorine levels get too high. There are three main types of chlorine available for shocking your pool. Two of these shocks are chlorine-based, while one kind is not.

Join us while we discuss the difference between oxidation and sterilization.

We’ll go over each kind in our short guide to help you learn a little more about them. We’ll list all the pros and cons so you can make an educated purchase.

We’ll also look at cost, ease of use, and how each of these chemicals affects the balance of other chemicals in your pool.

Types of Shock

There are several types of shock commonly used in pools, hot tubs, and spas. Calcium hypochlorite, dichloroisocyanuric acid, sodium monopersulfate, and bromine. You can break these types of shock into chlorine-based shocks and non-chlorine based shock to help get a better understanding of how they work.

Chlorine Shock

These are the different types of chlorine-based shock.

Calcium Hypochlorite

Calcium hypochlorite is the most popular type of shock in use today for all pools. If you bought shock for a chlorine pool without specifying which kind you wanted, you purchased calcium hypochlorite. This kind of shock is the least expensive and also the most powerful.

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Calcium hypochlorite attacks organic materials as well as bacteria. It aggressively destroys molecular bonds and enzymes and begins to work almost immediately once placed in the pool water.

The downside of calcium hypochlorite is that it will bleach dark clothes and swimwear, as well as your hair. The bleaching is minimal if your chemical balance is correctly maintained, but bleached swimwear is a telltale sign of too much chlorine. As chlorine breaks down bacteria and organic materials, it leaves behind a chemical called combined chlorine, and if the number of combined chlorine gets too high, you need to shock your pool to get rid of them. Combined chlorine causes the chlorine smell you may be familiar with, it may also lead to burning eyes and itchy skin.

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Calcium hypochlorite is also dependent on the amount of stabilizer in the water. The stabilizer is known as Cyanuric acid, and too little of this will cause the chlorine to burn up quickly in the sunlight, but too much will reduce the chlorine’s ability to sterilize the water. Though it will clean any water, warmer water will burn off calcium hypochlorite very quickly, so it’s better for pools than a spa or hot tub.

Dichloroisocyanuric Acid

Dichloroisocyanuric acid is the main ingredient in ordinary household bleach. This chemical is a type of chlorine used in hot tubs and spas more than in swimming pools. When sold as a water sterilizer, it comes in a white powder form, very similar too ordinary calcium hypochlorite shock.

Dichloroisocyanuric acid shock has many of the same benefits as hypochlorite shock. It attacks and destroys organic material as well as bacteria. As its name suggests, this chemical also contains cyanuric acid, so you don’t have to worry so much about stabilizer when you use this type of shock. It also handles higher temperature water much better than calcium hypochlorite.

The downside to dichloroisocyanuric acid is that it works much slower than calcium hypochlorite, and because it contains stabilizer, it’s easy to get too much stabilizer in your swimming pool. There is no way to remove cyanuric acid from your water except to replace it with fresh water. You can also experience burning eyes and itchy skin like you do with calcium hypochlorite

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You replace the water much more often in a spa or hot tub then you do in a swimming pool, so you can use this type of shock in that situation. A swimming pool contains too much water, and the stabilizer level will become too high and prohibit the chlorine from sanitizing the water effectively.

Bromine

Bromine is another type of chlorine-based shock, and it behaves differently than the others. Adding bromine doesn’t affect your pool pH as much as chlorine does, and it kills bacteria a lot longer than calcium hypochlorite will. It’s the slowest acting of all the chlorines, but it’s the most stable in warm water. Bromine is the most popular shock to use in hot tubs and spas.

The downside to bromine is that it burns up quickly in the ultraviolet rays of the sun, and unlike calcium hypochlorite, the stabilizer cyanuric acid does not work here, and the bromine will dissipate rapidly on a sunny day. Another downside is its slow reaction time, and when combined with its quick dissipation from ultraviolet light, it can allow algae and bacteria to grow in your swimming pool. Keeping your bromine levels high enough will be difficult even in a spa or hot tub exposed to the sun. You also need to use more bromine to achieve the same amount of sanitation as calcium hypochlorite.

Non-Chlorine Shock

Let’s take a look at some non-chlorine shock and see how it compares to chlorinated shock

Sodium Monopersulfate

One of the biggest advantages of sodium monopersulfate is that it doesn’t create any odor. Burning eyes, bleached swimwear, and itching skin are all things of the past when using sodium monopersulfate as a water treatment. This type of shock is not affected by ultraviolet light from the sun, nor is it affected by water temperature. There is no combined chlorine, also called chloramines, created as a result of using sodium monopersulfate as a water treatment.

The downside to sodium monopersulfate is that it doesn’t sterilize the water or kill any bacteria, it only oxidizes organic material in the pool. Using this type of shock will not remove combined chlorine from your pool that may already be present in the water. It can also bring down the pH of your pool, reducing the effectiveness of other chemicals

Conclusion

We recommend using the standard calcium hypochlorite as your pool shock unless you have some reason not to. Calcium hypochlorite is the most effective at killing germs and removing organic compounds, even in warm water. Keeping your chlorine, stabilizer, pH, and other chemicals balanced in your pool will minimize the side effects of chlorine, like burning eyes, bleached swimwear, and itchy skin.

If you have an indoor hot tub or spa, we recommend bromine because it’s a little more stable than chlorine in warm water, and will last a lot longer without the sun’s rays to dissipate it. If you are allergic to calcium hypochlorite or chlorine-based pool shocks, you will need to use sodium monopersulfate, but you will still need to find and anti-bacterial to sterilize the water.

We hope you have enjoyed reading if we have helped clear up the difference between chlorine-based shock and non-chlorine shock, please share this short guide on Facebook and Twitter.

Featured Image: Pool Super Shock Treatment/HTH, Amazon