The ABC’s of Shocking Your Swimming Pool
Why is Shock needed?
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Shocking your swimming pool is an important part of keeping your pool water clean. Shocking is the act of adding chlorine to your pool to raise your pool’s chlorine level quickly and at much higher rates than normal, otherwise known as super-chlorinating. Normal chlorine levels in a swimming pool are between 1-3 ppm, shocking your pool, raises your chlorine level to between 5-10 ppm. Shocking a pool destroys a certain type of chlorine in the pool water.
Swimming pool disinfection
In swimming pools, chloramines are formed by the reaction of free chlorine with organic substances, such as urine and sweat. Chloramines, compared to free chlorine, are both less effective as a sanitizer and, if not managed correctly, more irritating to the eyes of swimmers. Chloramines are also responsible for the reported “chlorine” smell of swimming pools. Some pool test kits designed for use by homeowners are not able to distinguish free chlorine and chloramines, which can be misleading and lead to non-optimal levels of chloramines in the pool water. There is also evidence that exposure to chloramine can contribute to respiratory problems, including asthma, among swimmers. Respiratory problems related to chloramine exposure are common and prevalent among competitive swimmers.
From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Chloramine#Swimming_pool_disinfection
Adding shock destroys chloramines that have formed in your pool’s water. Chloramines prevent your pool’s existing chlorine from sanitizing properly and burning off any organic matter in your pool water. Organic matter is what algae use for food in order to grow, so ridding your pool of this helps prevent the formation of algae.
Before I Shock My Pool?
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Chlorine works best when the pool water chemistry pH is within range. If you are going to shock your pool it is good practice to get the pH levels down to the lower end of the scale before adding the shock. The shock will raise the pH of your pool water when added. Starting the pH level at the lower end will ensure that the chlorine works at top efficiency the longest.
One more thing
Pool Chemistry control can fail if there is a problem with filtering or pumping your pool water. It is best practice to start with a clean filter and a pump that is running at maximum efficiency. After all, you need to filter out organics from your pool water and distribute the chlorine to every gallon in the pool.
Safety first
For safety, no swimming immediately after shocking. In fact, close the pool for swimming for 8 hours after shocking the pool. This is due to the extreme level of chlorine in the pool water.
When should you shock?
The sun’s UV rays destroy unstabilized chlorine. So, to get the best results it is best to shock before sunset. This way the shock can “work” at top efficiency. The short answer to when should I shock my swimming pool is “when it needs it”. Any time that an event introduces organics into your pool water(rain, high winds) or the conditions make growing algae ideal(high temperatures, lots of swimmers) you can watch your chlorine levels plummet. These are conditions that will require shocking your pool to clear chloramines and get your pool chemistry back in control.
What Types of Shock Are Available?
Granular Shock: Granular or powdered oxidizers come in 4 types and 6 strengths.
In The Swim Sodium Di-Chlor Chlorine Granular Pool Shock – 40 Pound Bucket
Granular 
- Cal Hypo
- Dichlor
- Potassium Monopersulfate a non-chlorine shock
- Lithium Shock
Liquid Shock
- Liquid Shock: Sodium Hypochlorite strength ranges from 5% for store brands to a 12.5% commercial strength bleach.
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Each of these shocks have distinct advantages and disadvantages. The choice is yours based on availability, cost, preference. If you buy liquid bleach for your pool, be sure to get unscented, regular bleach.
How Much Shock Do You Need?
Exact dosages of chlorine will depend upon your pool size and the type of chlorine you use for shock, but a good rule of thumb is 1 lb. of granular shock per 10,000 gallons of water. If you are using liquid chlorine shocking your swimming pool, you want to use 3½ quarts per 10,000 gallons of water.
Don’t know how many gallons your pool has? For shocking your swimming pool you need to know how many gallons your pool holds. Here is a pool volume calculator that can determine your pool size. Measure your pool’s length, width, depth and round to the nearest foot. If your pool is free form divide the pool into sections and enter each section to get an accurate estimate.
How Do I Shock My Pool?
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Granular shock can be broadcast across the pool surface for a white gunite/plaster pool. For Vinyl or fiberglass pools or black gunite/plaster pools, mix and dilute the shock with water. This will prevent bleaching when adding it to your pool. Dilute liquid chlorine before adding to your pool.
To dilute, fill a bucket with pool water and then add your liquid or granular chlorine. Mix it up and then pour the solution over the surface of your swimming pool. Be aware that any splash on your clothing will probably bleach it so dress appropriately. Be sure to use gloves and protect your eyes, wear safety glasses with side shields.
How Often Should I Shock My Pool?
The answer to how often to shock your pool is “whenever your pool needs it.” The answer assumes that you are observant of your pool and the conditions it is experiencing every day. Shock your pool more frequently in the following situations:
- Whenever you see algae start to form.
- A long stretch of extremely hot weather.
- If you see your pool water start to get hazy.
- After a heavy rain storm or windstorm.
- If your pool has seen extensive use.
There you have it. The why, when, what type, how much, how do I, and how often should I questions answered about shock. Now that you have all the information on The ABC’s of Shocking Your Swimming Pool you know how to keep that water crystal clear.
Related Article: Hard Lessons Learned on Pool Water Chemistry
Additional Article: Clear sparkling pool water strategy
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