An at-home swimming pool or hot tub is a fun and valuable amenity. Still, routine pool maintenance is crucial to keep the water clean and clear. In this article, find out how to shock a pool, why it works, and when to do it.
Chloramines naturally form in your pool water when chlorine binds to oils, sweat, and other contaminants in the water. They’re also called “combined chlorine.”
They produce a strong chemical smell and can irritate eyes, skin, and respiratory systems. Properly balanced pool water doesn’t have much of an odor.
The term “shocking” refers to raising the amount of free chlorine, or chlorine that hasn’t yet dissolved in the water, by mixing chlorine or other chemicals into your pool water.
How often to shock your pool depends on the usage levels at different times of the year. Read on to learn all about safely using pool chemicals to keep your home swimming pool in prime condition.
How Often Should You Shock Your Pool?
New pool owners sometimes wonder, “How often should you shock your pool?” It depends on how much it gets used.
During the summer months when you’re swimming in it regularly, apply pool shock every week or two. During other seasons when pool activity levels are lower, shock your pool once per month.
When you use a pool test kit, you measure chlorine and pH levels. Make sure you have FAS-DPD test strips that measure free chlorine levels, not just total chlorine. The optimal free chlorine range is between 1.0-3.0 ppm.
The purpose of shocking your swimming pool is to increase the free chlorine levels and eliminate contaminants like chloramines, bacteria, and algae growth. This process is sometimes called breakpoint chlorination. It’s a great way to clean a green pool fast.
Chlorine is most effective when water pH level is between 7.2-7.8. Acidic water (lower than 7.0) is harmful to swimmers and the swimming pool itself. With a pH level above 8.0, chlorine quickly becomes less effective. Use a pool test kit to monitor alkalinity.
Chlorine also loses potency when exposed to sunlight. Some outdoor pool owners add cyanuric acid to their pool water. It acts as a stabilizer to help the chlorine last longer by protecting the free chlorine from ultraviolet rays.
Keep in mind that pool shocking chemicals are not the same as flocculants and clarifiers. Pool water clarifier consolidates particles in the water into small clumps so the pool filter can catch them better. Regularly clean your pool filter with a hose or a DIY pool filter cleaner to remove debris.
Flocculants coagulate debris into large clusters that sink to the pool floor for easier manual removal with a skimmer or pool vacuum.
Types of Pool Shock Treatments
There are four primary types of pool shock chemicals: calcium hypochlorite, sodium dichlor, lithium hypochlorite, and potassium monopersulfate. Each serves a different purpose. It’s crucial to know the differences between them and understand when to use each one.
Calcium hypochlorite, or cal hypo, is the strongest and fastest-acting pool shock treatment available. A granular, calcium-based pool shock, it dissolves quickly in pool water.
However, it’s unstabilized, meaning it doesn’t have added cyanuric acid, so it’s best to use it at night for outdoor swimming pools.
Depending on the hardness of your water, cal hypo may leave the water a bit cloudy. Cal hypo isn’t suitable for fiberglass, vinyl, pebble tec, or painted pools, as it may bleach the surface.
Sodium dichlor is a sodium-based granular pool shock. It dissolves rapidly and doesn’t typically cloud the pool water. This type of pool shock is safe for all pool materials, as well as saltwater pools and spas. It contains added cyanuric acid, making it stable in sunlight.
Unlike cal hypo, lithium hypochlorite is safe to use on fiberglass and vinyl pools. It’s a powdered chlorine product that’s both a pool shock and sanitizer. It’s unstable, without any extra cyanuric acid.
For a non-chlorine shock treatment, many pool owners use potassium monopersulfate, or MPS. This technique oxidizes the water, destroying contaminants and making the existing free chlorine more effective. It doesn’t change the water’s cyanuric acid levels and is safe to use any time of the day.
Pool care experts frequently recommend that pool owners alternate between using a chlorine shock and a non-chlorine shock for the best results to reduce the amount of chlorine accumulating in your pool water, keeping the combined chlorine level lower.
How to Shock a Pool
The application methods for each type of pool shock are different, so be sure to follow the instructions printed on the product package carefully.
Always use safety equipment like gloves, safety glasses, and a respirator mask when handling pool chemicals. Ensure your pool pump is running when you add the shock treatment.
Calcium hypochlorite must be pre-mixed before adding it to your pool. Start the process at dusk, and allow eight hours for it to work.
Sodium dichlor and lithium hypochlorite don’t usually need to be dissolved ahead of time. Both chemicals must be applied at night.
Potassium monopersulfate is safe to use at any time of day. MPS is ideal to use in combination with bromine or chlorine sanitizers.
Can You Use Bleach to Shock a Pool?
Chlorine bleach works as an effective DIY alternative to name-brand pool shock chemicals. The active ingredient in most pool shocks and chlorine bleach is sodium hypochlorite.
Pool shock chemicals contain approximately double the concentration of sodium hypochlorite that household bleach does.
Clorox recommends a dilution rate of a half-cup of bleach per thousand gallons of water. As with other pool shocks, apply the bleach after dark.
How Long after Shocking Pool can You Swim?
It’s critical to wait before using your swimming pool again after shocking the water. How long to wait after shocking pool depends on which type of chemicals you use.
Chlorine levels at or below 5 ppm are for safe swimming. Water that’s too chlorinated causes eye, skin, and respiratory irritation.
For chlorine pool shock, wait at least eight hours before swimming. A non-chlorine shock is sometimes called the “shock and swim” method because it’s safe to swim after about 15 minutes.
Does Shocking Your Pool Kill Algae?
While shocking your pool water normally clears up algae growth, it sometimes doesn’t fully eliminate a severe algae problem. In that case, it’s helpful to add an algaecide to your pool water after the initial shock treatment to kill any remaining algae cells.
Most commercially sold algaecides are copper-based and work by disrupting the algae’s natural cellular processes. For a DIY alternative to expensive name-brand algaecide products, try making it at home.
To get rid of algae on bottom of pool, blend the baking soda and Borax in a small container, then pour in just enough bleach to create a thick paste. Spread it on your pool brush and thoroughly scrub all surfaces.
The chlorine in the bleach kills algae and bacteria. The Borax and baking soda eliminate stains and loosen algae roots from the walls and floor. Baking soda also slightly increases the pH of your pool water, so be sure to test the pH afterward.
Is Cloudy Pool Water after Shocking Normal?
Sometimes your pool water appears cloudy after a shock procedure. This isn’t unusual, especially if your pool water has high calcium levels. Just keep your pool filter running, and it typically dissipates within 24 hours.
If the water doesn’t clear up after a day or so, get out your test kit. High alkalinity, chlorine, or pH levels may cause excessively cloudy pool water after shocking, as does calcium hardness. Balancing your pool chemicals is crucial for healthy and clean pool water.
What Does Pool Shock Do?
Shocking your pool water is a crucial part of routine pool maintenance and the best way to remove calcium from pool tile walls. When the amount of chloramines in the water is higher than the free chlorine levels, the pool water gets an unpleasant chlorine smell and may cause irritation to some swimmers.
In addition to eliminating chloramines, keeping enough chlorine in the water is vital for sanitary pool water. It helps to maintain a pool and minimizes the buildup of harmful contaminants. Shock the pool when combined chlorine levels rise above 0.5 ppm.
Have you ever asked, “How often should you shock your pool?” As a general rule, apply a shock treatment every week or two during the summer and once monthly when you’re not using your swimming pool as frequently.
Cloudy pool water after shocking is normal and usually clears up within 24 hours if you leave your pool filter running.
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