What does “Shocking” a swimming pool mean, and why is it necessary?
Your swimming pool needs to be “Shocked” at least once each week, or more. You should shock more frequently if the pool is used heavily, after you receive large amounts of rain, or during extended periods of hot, sunny weather. Click here to shop for quality pool shock chemicals at competitive prices. The chlorine tablets or granular chlorine that you constantly dissolve into your pool water seeks out and combines with bacteria and other organics on a molecular level, to neutralize these harmful contaminants. In the process of killing these harmful contaminants the chlorine becomes inactive, and the chlorine and bacteria that have combined together is called “Combined Chlorine”. The combined chlorine must be removed from the swimming pool to keep your pool water safe and clean. The combined chlorine is removed by “Shocking” the swimming pool. Super chlorinating or “Shocking” means drastically raising the chlorine level of the swimming pool for a short time, to a high enough level that the combined chlorine is burned up.
Which pool shock should you use?
There seems to be a very wide selection of swimming pool shock on the market, and each pool supply distributor works hard to make their product seem a step above the rest. When all of the products are compared side by the side, the only real difference on the labels is the concentration of the active ingredients in the product. The standard pool shock that most pool owners use has the active ingredient Calcium Hypochlorite. You should expect the label to read 65% Calcium Hypochlorite. Another more concentrated version of the pool shock may have as much as 75% Calcium Hypochlorite. Some manufacturers advertise a Calcium Hypochlorite based shock product which allows you to swim in the pool shortly after adding it. Upon examining the label you will notice that the concentration of Calcium Hypochlorite is only around 47%. Although you can swim shortly after using this type of shock product, the lower concentration of Calcium Hypochlorite may not be enough to effectively destroy bacteria and harmful contaminants in your pool.
In addition to the Calcium Hypochlorite (chlorine) based pool shock, you will find a product called Chlorine-Free Pool Shock. This revolutionary pool chemical performs the same task of oxidizing bacteria and organics in your swimming pool water, but it does not contain any chlorine or harsh chemicals. Chlorine-Free shock performs just as well as a chlorine based swimming pool shock by using the active ingredient Potassium Monopersulfate. Chlorine free shock uses a unique chemical process to destroy bacteria, instead of raising the chlorine level of water to dangerous levels. You can actually swim in the pool only one hour after using Chlorine-Free Shock. Chlorine based pool shock (Calcium Hypochlorite) has a high pH, and will naturally raise the pH level of your swimming pool water, in addition to changing your chlorine level. Chlorine free shock has a neutral pH, and will not affect any of your pool chemical levels.
Chlorine-free shock is also superior to chlorine based pool shock for normal weekly shocking because of the inert ingredients and fillers that are used in the product. Each time chlorine based (Calcium-Hypochlorite) swimming pool Shock is added to your water, you are adding calcium to the pool. This may eventually raise the calcium hardness level of the water, causing cloudiness or scaling along the water line. A high calcium hardness level may cause even larger problems in swimming pools that are initially filled with hard water that already has a high concentration of calcium.
Chlorine based swimming pool shock should always be kept on hand, because it is the ONLY pool chemical that will kill algae after algae has grown in the pool. If your water chemistry is properly maintained, and you shock your swimming pool at least once a week, you will never see algae or experience water problems of any kind!
Another chlorine based shock product that most pool supply distributors offer is commonly referred to as “Lithium Shock”. Rather than the active ingredient Calcium Hypochlorite that is found in common Pool Shock, Lithium Shock contains Lithium Hypochlorite. Lithium shock uses lithium as a filler instead of the calcium, which makes this product dissolve in water much quicker and does not affect the calcium hardness level of the swimming pool. Although Lithium Shock is superior to the common Calcium Hypochlorite based pool shock, this product is not used by most pool owners because of the higher cost.
Don’t use Liquid Shock!
Another type of shock that is widely available at any local pool store, hardware store and many grocery stores is liquid chlorine. This liquid chlorine is commonly used as shock, and used in place of chlorine tablets. Many pool owners believe this liquid chlorine is all they need to properly maintain a swimming pool, and unfortunately this is incorrect. Liquid chlorine is very inefficient and costly compared to properly maintaining a swimming pool using chlorine tablets and a weekly shock treatment. Liquid shock may seem easier to use than the granular shock for some pool owners because you simply walk up to the pool and dump the liquid in. The problem is that after you dump the hazardous liquid in your pool, you have to dispose of all the empty plastic bottles with the dangerous chemical residue inside. Granular pool shock is packaged in small, easy to use 1 lb. bags. If any children have access to the area where pool chemicals are stored it will be far easier to have an accident involving full or empty bottles of liquid chlorine, than an accident with bags of granular pool shock.
Granular Pool Shock is rated at a minimum of 47% available chlorine and available in concentrations up to 75%. If you look at the label on a bottle of liquid chlorine it will say that it is ONLY 10% SODIUM Hypochlorite (chlorine)!! This means you are paying for 90% salt water with every bottle you buy. The dosage for a standard granular pool shock is 1 lb. per 10,000 gallons of pool water. If you are currently using a liquid shock, you should compare the cost of a dose of liquid shock to the cost of a dose of granular pool shock. You will find that granular pool shock can offer you a considerable savings.
How to shock your pool:
Now that you know why you need to shock your pool, the next question is how do you shock your pool. Before any shock is added to your swimming pool water the chemical must first be pre-dissolved in water. All forms of pool shock are granular, and should dissolve relatively quickly in water. The first step is to fill a 5 gallon bucket with water from the pool and slowly pour the granular shock into the bucket of water (NEVER add water to a chemical, always add chemicals to water). Stir the bucket well and agitate the water for one minute or more to dissolve the pool shock. With the filtration system running, slowly pour the bucket of dissolved shock directly in front of the return line fitting. You will see the dissolved shock water being carried out into the pool by the jet of water coming from the return line. Pour slow enough that all of the water coming from the bucket is carried out into the pool, and does not settle to the pool floor. When you near the bottom of the bucket (down to about 1/4 left in the bucket) you should fill the bucket back up with pool water and stir it again for one minute or more. There will be shock granules at the bottom of the bucket which did not dissolve the first time, and if you have a vinyl liner in your swimming pool you do not want any undissolved shock to settle to the floor.