To keep your pool sanitized and free of algae, shocking should be a regular part of your maintenance routine. If you’re a newer pool owner, you may not be sure what exactly it means to shock your pool. You may also wonder how frequently you should be doing it.
There are several different chemicals available, some of which call themselves pool shock. Each will affect your pool slightly differently but with the same fundamental purpose: restoring the levels of free chlorine in your pool which naturally decay over time.
Ultimately, there are some key facts you should know before deciding which pool shock to use, how to use it, and how frequently to shock your pool thereafter.
First, a Quick 101 on How Chlorine Works
The free chlorine in your pool works to sanitize the water by catching and oxidizing organic matter. In the process of sanitation, the chlorine produces a new chemical compound called chloramine. It is, in fact, chloramine that produces the distinctive chemical smell that people often misattribute to chlorine.
Since free chlorine is used up in the process of oxidizing organic matter, the levels of chlorine in your pool will naturally decrease over time. A level of free chlorine that is too low will mean your pool is not being sanitized properly and can leave it susceptible to contamination or algae growth.
A pool that has too much chloramine and not enough chlorine will smell irritating, is not being sanitized properly, and needs to be shocked.
The CDC recommends a free chlorine level of 1 part-per-million (ppm) for swimming pools, and we recommend that you aim for between 1 and 3 ppm. If your pool falls below this level, it’s time to shock it.
What Does It Mean to Shock a Pool?
Shocking simply refers to the process of quickly adding a lot of chlorine to your pool (around 2-10 times normal) for a brief period of time. This high level of chlorination will sanitize your pool and allow the free chlorine to return to desired levels.
This can be accomplished with a few commonly marketed chemicals, among the most common being sodium hypochlorite (sometimes called liquid chlorine), calcium hypochlorite (cal hypo), and Dichlor Shock.
The type of shock you use will depend on what’s available to you, the nature of your pool, and your personal preferences. Regardless of how you get there, maintaining at least 1 ppm of free chlorine is your goal.
What Are the Different Types of Pool Shock?
A few of the chemicals commonly used for shocking pools are:
- Sodium Hypochlorite: This is the same chemical marketed as “bleach,” but you’ll want a stronger, more concentrated version marketed as liquid chlorine.
- Calcium Hypochlorite: This is a dry chemical compound that needs to be dissolved before you put it in your pool.
- Dichlor Shock: This product is generally designed for use in saltwater pools.
Liquid chlorine is generally the most inexpensive and readily available option. The main drawback is that it contains less chlorine than the other products, so it may be a less effective sanitizer. Still, when used regularly and properly, it should be good enough for use in most home swimming pools.
Calcium hypochlorite, sometimes called Cal Hypo, is a dry version of chlorine that you must first dissolve into water before putting it in your pool. Cal hypo contains a high amount of chlorine which makes it very effective at shocking pool water. However, it will also raise the levels of calcium in your pool. If you live in an area with hard water, you may want to choose another option.
Dichlor Shock is a name used to market more than one chemical. The defining features of these different products are their sodium base, as opposed to cal hypo’s calcium base, and their dry state. Thanks to its sodium base, Dichlor Shock is best for use in saltwater pools.
When To Use an Unstabilized Chlorinator
No matter the product you use to shock your pool, the point of shocking is to raise the levels of free chlorine to very high levels and then have them fall back down after about 8 hours to a day.
Some chlorination products include chemicals that work to “stabilize” the chlorine, which helps maintain the existing levels of free chlorine. These products have their uses but should be avoided when shocking your pool since you don’t want free chlorine levels to remain too high for too long.
Another effect of stabilizers is to protect chlorine from the sun’s UV rays which can destroy it. Since you should be using unstabilized chlorine, it’s important to shock a pool at night so UV rays don’t ruin your treatment.
How Often Should You Shock Your Pool?
For maintenance, we recommend shocking your pool around once per week to every two weeks. This may increase or decrease depending on how frequently the pool is used. It’s best to use once a week as a general guide and adjust according to your needs.
Other indicators that your pool may need a shock treatment are:
- Heavy Use: A pool party or long weekend may necessitate a shock.
- Prolonged Intense Sunlight: As mentioned earlier, sunlight can lower free chlorine levels.
- Rain: Rain can introduce other contaminants that may overwhelm your pool’s free chlorine.
- Strong Smell: The smell of chloramine is very distinctive. Most people attribute it to chlorine. If your pool smells irritating, it is time for a shock treatment.
- Green or Cloudy Water: A pool that isn’t clear will need to be cleaned and probably shocked.
- Algae: Finally, algae are a clear indicator that a shock is necessary.
The Benefits of Shocking Your Pool
During the warm seasons, regular shocking of your pool is necessary to keep it sanitized against the natural buildup of organic waste. While the need for shocking can be lessened with proper hygiene and by keeping unnecessary contaminants out of the water, the levels of free chlorine in your pool will naturally fall over time.
Maintaining a proper chlorine level while the pool is in use will keep the pool clean, free of algae, and ready for use. Don’t neglect shocking your pool before closing it for the season as well. This can help excessive algae buildup and save you some cleaning when it’s time to open your pool back up again. We recommend making weekly “shocking” a part of your regular pool maintenance routine.
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