SHOCK: Technically speaking, "shocking" a pool and "superchlorinating" a pool have different meanings. By official definition, "shock" means to add a NON-CHLORINE compound (usually Potassium Peroxymonosulfate) while "superchlorinate" means to add mega-doses of a CHLORINE-BASED compound (usually Calcium Hypochlorite or Lithium Hypochlorite). If you really breakdown the definition of "superchlorinating" and apply it to the definition of "shocking," you will see many similarities with the two terms. Therefore, poolmanual.com recommends that pool owners neglect the "technical" differences of the two terms and view "shocking" and "superchlorinating" as one-in-the-same. Most pool professionals are only taught, "shocking" and usually speak just of "shocking" anyway. Therefore throughout this manual, the process will only be referred to as "shocking the pool," regardless of the type of shock that you use.
For more specific information on shock, refer to the following topics:
WHY SHOCK WITH CHLORINE: Chlorine is very effective at killing bacteria, living organisms, and other contaminates (which again are dirt, debris and algae spores), but when ammonia is present, chlorine will combine with it, but cannot successfully kill it, and the two combine to form "Chloramines." Chloramines will remain in the water, and will register as chlorine, but are ineffective at sanitizing, disinfecting, or oxidizing the pool water.
Ammonia is commonly present in pool water from either environmental factors, a build up of fertilizers that are carried by wind and dropped into pools, from swimmer wastes (perspiration, urine, saliva and body oils), or even from some suntan lotions. No matter how ammonia enters a pool, it will exist.
So then, since Chloramines are ineffective and undesired forms of chlorine, how are they removed from the water? Easy - by shocking the pool on a consistent and regular basis. Even if you maintain a 2.0 - 3.0 ppm (ideal) chlorine reading at all times by merely adding either chlorine tablets or granular chlorine to the pool, the presence of ammonia will lead to Chloramines, preventing the chlorine from being fully effective. The only way to combat Chloramines, and kill ammonia, is by shocking the pool.
There is a constant debate in the pool industry as to when to shock the pool. But, there is absolutely no debate on the importance of shocking the pool. The continual additions of chlorine, in association with routine shocking, is the only way kill all the bacteria, living organisms, ammonia, and other contaminates that invade your pool. The majority of chlorine users shock with either Calcium Hypochlorite or Lithium Hypochlorite, which are both chlorine-based shock. It is best to shock your pool in the evening for two reasons:
Chlorine users can also use a non-chlorine shock from time-to-time. A benefit of non-chlorine shock is that you can swim within 15 minutes after its addition. So, if you use chlorine and you are having a party, but the water is a little hazy, you can add some non-chlorine shock to clear the pool for the party. But, if you use non-chlorine shock with a chlorine pool, it is only temporary. You had better test and adjust the Free chlorine reading and then shock the pool with a chlorine-based shock within 24-48 hours-especially since the bather load associated with a pool party is typically large, and the water already looked a little hazy to begin with.
WHY SHOCK WITH BROMINE: Bromine is very effective at killing bacteria, living organisms, and other contaminates (which again are dirt, debris and algae spores), but when ammonia is present, bromine will combine with it, but cannot successfully kill it, and the two combine to form "Bromamines." Bromamines will remain in the water, and will register as bromine, but are not as effective at sanitizing, disinfecting, or oxidizing as is actual bromine.
Ammonia is commonly present in pool water from either environmental factors, a build up of fertilizers that are carried by wind and dropped into pools, from swimmer wastes (perspiration, urine, saliva and body oils), or even from some suntan lotions. No matter how ammonia enters a pool, it will exist.
So then, since Bromamines are not real effective, how are they removed from the water? Easy - by shocking the pool on a consistent and regular basis. Even if you maintain a 2.5 - 4.0 ppm (ideal) bromine reading at all times by merely adding bromine to the pool, the presence of ammonia will lead to Bromamines, preventing the bromine from being fully effective. The only way to combat Bromamines, and kill ammonia, is by shocking the pool.
There is a constant debate in the pool industry as to when to shock the pool. But, there is absolutely no debate on the importance of shocking the pool. The continual additions of bromine, in association with routine shocking, is the only way kill all the bacteria, living organisms, ammonia, and other contaminates that invade your pool.
The majority of bromine users shock with Potassium Peroxymonosulfate, which is almost universally packaged and sold as "non-chlorine shock." A drawback is the expense of non-chlorine shock. A benefit of non-chlorine shock, though, is that you can swim within 15 minutes after its addition. Since we now know that chlorine is often an ingredient in bromine, you bromine users can certainly supplement non-chlorine shock for a chlorine-based shock from time-to-time, especially if the water is cloudy or murky. Many bromine users will use their non-chlorine shock regularly, but once every 1-2 months, they will supplement their pool water by adding a chlorine-based shock instead. If you use a chlorine-based shock, it is best to shock your pool in the evening for two reasons:
For the most part, though, if you use bromine, shock with a non-chlorine shock. The non-chlorine shock will oxidize the ammonia, and at the same time, it will reactivate the existing bromine to continue sanitizing and disinfecting the water.
WHY SHOCK WITH ALTERNATIVES TO CHLORINE: It does not matter which sanitizer/disinfectant/oxidizer that you use-whether it be chlorine, bromine, or any of the various alternatives on the market, such as Bacquacil, mineral systems, chlorine generators (which make chlorine from salt), iodine, or flourine-you will still need to shock your pool. Although the alternatives can kill bacteria, living organisms, and other contaminates (which again are dirt, debris, or algae spores), they likewise cannot successfully kill ammonia alone.
Ammonia is commonly present in pool water from either environmental factors, a build up of fertilizers that are carried by wind and dropped into pools, from swimmer wastes (perspiration, urine, saliva and body oils), or even from some suntan lotions. No matter how ammonia enters a pool, it will exist.
So then, since ammonia is an invader of your pool's water chemistry, how is it removed from the water? Easy - by shocking the pool on a consistent and regular basis. Even if you maintain the recommended ideal range for the given alternative at all times, the presence of ammonia will lead to water chemistry issues and problems. The only way to kill ammonia is by shocking the pool.
There is a constant debate in the pool industry as to when to shock the pool. But, there is absolutely no debate on the importance of shocking the pool. The constant addition of your chosen alternative, in association with routine shocking, is the only way kill all the bacteria, living organisms, ammonia, and other contaminates that invade your pool.
If you have chosen an alternative to chlorine (other than bromine), you will need to consult with your pool professionals as to which type of shock to use. The pool professionals that sold you the alternative should have complete support materials to assist you with any of your sanitizing, disinfecting, oxidizing, and shocking needs.
TYPES OF SHOCK: To make it easy, shock can be divided into chlorine-based shock and non-chlorine shock.
There are three common types of chlorine-based shock:
There is really only one common type of non-chlorine shock:
CALCIUM HYPOCHLORITE: Calcium Hypochlorite is a popular and effective chlorine-based type of shock. It is always best to dilute Calcium Hypochlorite in a bucket of water, and then pour it into the pool-ALWAYS pour the chemical into the bucket of water; NEVER pour water over the dry chemical.
Calcium Hypochlorite has a 65%-68% available chlorine. Calcium Hypochlorite is slow dissolving. Since it has such a high chlorine-base, and since it is a slow dissolving granular compound, if not fully diluted in water first, it could bleach a pool floor. As with any chemical, read the instructions on the label before adding any Calcium Hypochlorite to your pool. As a guideline, add 1LB of Calcium Hypochlorite shock per 10,000 gallons of water under normal conditions. Add 2 LBS of Calcium Hypochlorite shock per 10,000 gallons of water under extreme conditions-a high amount of Chloramines, cloudy water, or the presence of algae.
You need to wait 8 hours to resume swimming after adding Calcium Hypochlorite shock (or any chlorine-based shock). If your pool is situated in a region with typically high amounts of calcium in the water, which can be monitored by testing the Hardness level of the pool water, then Calcium Hypochlorite shock is not the best option-the already high amount of calcium in the water coupled with the excess amount of calcium in Calcium Hypochlorite shock could very well lead to the formation of scale (a white, calcified deposit) on your pool walls and floor, or worse, in your plumbing or on your equipment. If you have hard water (high amounts of calcium or other minerals), use Lithium Hypochlorite shock.
NOTE: There has been a fairly recent addition to the market of a Calcium Hypochlorite shock that treats 15,000 gallons per LB versus 10,000 gallons per LB. So, if you have a 30,000 gallon pool, you would only need 2 LBS of this shock instead of 3 LBS. The price per LB is higher, but when you consider the price per gallons treated (which is what you should be considering), this newer Calcium Hypochlorite shock is the best option. Its quicker dissolving characteristics allow it to treat more gallons; its quicker dissolving characteristics are also safer for your pool structure, lessening the fear of bleaching the floor. Discuss the availability of this shock in your area with your local pool professionals.
LITHIUM HYPOCHLORITE: Although not as widely used as Calcium Hypochlorite, Lithium Hypochlorite is also an effective chlorine-based type of shock, particularly for those regions with typically high amounts of calcium in the water. Calcium Hypochlorite, as the name implies, uses calcium, which, if used in pools with hard water characteristics, the formation of scale may (and probably will) build up on the pool walls and floor, and perhaps inside the plumbing or on the equipment. If hard water exists, primarily due to the presence of calcium, use Lithium Hypochlorite as the shock.
Lithium Hypochlorite is quick dissolving, so it will dissolve completely before it even reaches the bottom of the pool, leaving little-to-no fear of bleaching the floor. Other than for those pools in regions with hard water (due to high levels of calcium), this quick dissolving characteristic is the primary benefit of Lithium Hypochlorite shock.
A drawback of Lithium Hypochlorite is that it is considerably more expensive than Calcium Hypochlorite. Since it only has a 35% available chlorine, more will be needed than compared to Calcium Hypochlorite-heightening an already high cost.
As with any chemical, read the instructions on the label before adding Lithium Hypochlorite. Some manufacturers recommend diluting it in water first and then pouring it into the pool, while other manufacturers recommend broadcasting it directly from the packaging. As a guideline, add 2 LBS of Lithium Hypochlorite shock per 10,000 gallons of water under normal conditions. Add 3 LBS of Lithium Hypochlorite shock per 10,000 gallons of water under extreme conditions-a high amount of Chloramines, cloudy water, or the presence of algae. Like Calcium Hypochlorite, you must wait at least 8 hours to swim after adding Lithium Hypochlorite shock
Although the cost of Lithium Hypochlorite is typically high, in regions with hard water (containing high amounts of calcium), the cost of Lithium Hypochlorite is offset by the cost of Calcium Hypochlorite plus Metal Sequestering Agents (to rid the water of the excess calcium), as well as the constant draining and refilling of the pool (water prices).
DICHLOR (GRANULAR CHLORINE): A powder form of chlorine, which is sometimes used a chlorine-based shock. Granular chlorine is a popular chlorine-based shock to help kill algae and for winterizing a pool.
Granular chlorine has a 63% available chlorine. Granular Chlorine is quick dissolving so there is a less chance that it will bleach the pool floor of any type of pool. . Since granular chlorine has high available chlorine and since it is quick dissolving, it can be used for both regular pool chlorination and for shocking a pool, all without adding any by-products to the pool water. Granular chlorine will not cloud the water upon initial application (which can occur with Calcium Hypochlorite). Granular chlorine has pH value of 6.8, which is near the desired pH range (7.2 to 7.8). Granular chlorine also possesses a built in Cyanuric Acid, which prevents the reduction of chlorine loss due to the sun. The only real drawback of granular chlorine is it's higher cost. Other than cost, granular chlorine has become a fairly popular shock for chlorine pools.
As a guideline, add 1LB of granular chlorine per 10,000 gallons of water under normal conditions. Add 2 LBS of granular chlorine per 10,000 gallons of water under extreme conditions-a high amount of Chloramines, cloudy water, or the presence of algae.
POTASSIUM PEROXYMONOSULFATE: Potassium Peroxymonosulfate, which is almost universally packaged and sold as "non-chlorine shock," is typically used with bromine. Once added, non-chlorine shock will oxidize the ammonia, killing Bromamines, while at the same time, reactivating the existing bromine, allowing it to continue to sanitize and disinfect the pool water.
Non-chlorine shock can also be used in a chlorine pool, but it will only oxidize ammonia, killing the Chloramines. It will not reactivate the existing chlorine in the pool, so it is ineffective at assisting the chlorine in it's sanitizing and disinfecting tasks. If a pool owner using chlorine is going to have a pool party, but the water is somewhat hazy, then non-chlorine shock can be added to oxidize the ammonia, killing Chloramines and temporarily restoring water clarity. This way, swimming can resume within 15 minutes, and it will hold your pool's water clarity until a sufficient dose of a chlorine-based shock (either Calcium Hypochlorite, Lithium Hypochlorite, or even granular chlorine) can be added. With the high bather load associated with a pool party, though, this chlorine-based shock had better occur within 24-48 hours after the party.
Although reentering the pool after only 15 minutes is a definite benefit of non-chlorine shock, its higher cost is an offsetting drawback. If non-chlorine shock is used, read the instructions on the label before it is added. Since non-chlorine shock is so quick-dissolving, most manufacturers recommend broadcasting it directly from the package and into the pool. But, some manufacturers do recommend diluting the non-chlorine shock in a bucket of water and then pouring it into the pool.
As a guideline, add 1LB of non-chlorine shock per 10,000 gallons of water under normal conditions. Add 2 LBS of non-chlorine shock per 10,000 gallons of water under extreme conditions-a high amount of Bromamines (or Chloramines), cloudy water, or the presence of algae.
SHOCK CHART: To summarize, the following chart is provided on shock:
| Product | Ph value | Available chlorine | By products | Form | Stability | Cyanuric Acid | Wait to swim | Dissolve Time |
| Calcium Hypochlorite | 11.8 | 65-68% | Calcium | Granular | Stable | 0 | 8 hours | Slow |
| Lithium Hypochlorite | 10.8 | 35% | 0 | Granular | Stable | 0 | 8 hours | Fast |
| Potassium Peroxymonosulfate | 2.3 | 0 | 0 | Granular | Stable | 0 | 15 minutes | Fast |
HOW TO SHOCK: Shocking a pool requires nothing more than reading the instructions on the label. The only way to add shock (and the only way to add any chemical is either by diluting the shock in a bucket of water and then pouring it into the pool or by broadcasting the shock directly from the packaging and into the pool. Here is a discussion of each:
NOTE: For an aboveground pool, reach over the wall, get close to the surface of the water, and pour the shock in random areas.
Regardless of the chosen shock compound, it is recommended to add only 1 LB at a time, repeating the process (diluting or broadcasting) until the full dosage of shock is added to the pool. And, regarding label instructions, here is a word of caution: some manufacturers (and pool professionals) recommend pouring shock directly into a skimmer. If you recall, we at poolmanual.com do NOT recommend placing or pouring ANY chemical into the skimmer(s).
WHEN TO SHOCK: "When" to shock is a question that is always asked, often eliciting numerous responses. In fact, "when" to shock the pool has been a constant debate in the pool industry. Some pool professionals will say once per week, some will say every other week, some will say monthly, and still others will say on an as-needed basis. One satisfactory answer given by a pool professional is that you only want to shock your pool when there is a build-up of ammonia and other undesired matter in the water that are handicapping the ability of your chlorine or bromine (or any other possible alternative) to effectively sanitize, disinfect and oxidize the pool water. Though a well-worded answer it does not effectively answer "when." Sorry to say, but there is no set, industry specific answer for pool owners as to when to shock. Relax-poolmanual.com will offer a general recommendation.
Shocking will vary due to the climate (primarily the temperature, humidity, and sunlight) and due to the bather load (the extent to which the pool is used-how many people use the pool at once, how many times throughout one day the pool is used, and how many days each week the pool is used). Here are suggestions:
This is a guideline ONLY. With your climate and with your individual bather load, you may have to shock more often than these general suggestions (or perhaps less than these general suggestions). It is virtually impossible to determine "limited," "normal," and "heavy" use of the pool. It is also virtually impossible to determine an agreed upon value for "cooler," "seasonal," and hot/humid" temperatures for the numerous regions. You have to decide your "use" and your current "weather conditions" and make your own decision. Consult your local pool professionals in your region (climate) for their recommendations on shocking. Also, keep these points in mind:
SHOCK IN THE EVENING: If you use non-chlorine shock, you can shock any time of the day or night. If you use a chlorine-based shock, then shock in the evening for (2) reasons:
SHOCK AND THE SOLAR COVER: Do NOT put your solar cover on your pool for at least 8 hours after shocking with a chlorine-based shock. The superchlorinated water will deteriorate the bubbles on the solar cover, rendering it less effective to draw in and retain heat.