The Shocking Truth About Shocking Your Pool

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The Shocking Truth About Shocking Your Pool

Every Central Florida pool owner knows about shocking their pool – or do they? Pool shocking is one of those pool maintenance necessities that most people assume they basically understand. How complicated can it be, after all? The truth is, there’s more to shocking your pool than dumping chemicals in it to quickly kill contaminants in the water. While Certified Leak Detection does not perform pool maintenance, we want you to get the most enjoyment from your backyard oasis – and of course, remember us if you ever suspect a pool leak!

Let us, therefore, take you through what pool shocking involves, which type of pool shock you need to use, and when and how to shock your pool.

What Exactly is Pool Shocking?

Pool shock is a granular oxidizer – a powdered form of chlorine used for the treatment of pool water. Shocking the pool is the act of adding chlorine or non-chlorine chemicals to your pool water to raise the free chlorine level to 10-30 ppm, which oxidizes or destroys algae, chloramines and bacteria.

Which Pool Shock Should You Use?

As a pool owner, it is crucial to know which pool shock you should use. There are many EPA-approved chemicals you can use to shock your pool. Your pool type, hard water issue, and high cyanuric acid would determine which pool shock you need to use for your pool. Here are some options:

Calcium Hypochlorite – Also known as cal hypo, calcium hypochlorite is the most affordable pool shock. You can get it in 65% and 73% strength, a pH level of 12, and is not stabilized. It provides excellent water clarity while destroying contaminants in pool and spa water, such as those found in sweat, urine and windblown debris. Aqua magazine provides a comprehensive description, instructions for use and cautions.

Sodium Dichlor – Also known as dichlor, sodium dichlor is a stabilized pool shock with cyanuric acid for sun protection. You get it in 56% strength with an almost neutral pH level. It does not add calcium to your pool.

Potassium Monopersulfate – Also known as non-chlorine shock, potassium monopersulfate oxidizes pool water in a chlorine-free formula that remains unaffected by sunlight, leaves no residue and adds only oxygen. 

Potassium monopersulfate is a strong oxidizer, and has the same oxidation potential as chlorine. There are numerous reasons people use this chemical to shock their pool – such as those who want to avoid chlorine.

Chlorine combines with swimmer and other organic wastes (nitrogen-based compounds) to form chloramines. These by-products are unpleasant and have a foul odor. Potassium monopersulfate also reacts with nitrogen-based compounds, but they don’t form chloramines because it does not contain chlorine.

One big advantage is that you can reenter the pool after a half-hour of adding the chemical. You usually have to wait 24 to 48 hours before reentering the pool if you shock it with chlorine. Also, the chemical dissolves quickly, and doesn’t fade pool liners. It also works fine with chlorine and allows chlorine to work more effectively as a sanitizer.

However, there are some disadvantages of using potassium monopersulfate. When it oxidizes urea and chloramines, nitrate ions are the primary oxidation product. Keep in mind that algae feed on nitrate. It can also lower the pH and total alkalinity of your pool. Moreover, this chemical is expensive. It is also crucial to know that the shock dose of 1 lb. per 10,000 gallons of water offer only 1/3 of the oxidizing power of 1 lb. of 65% calcium hypochlorite. And although this chemical is a strong oxidant, it is not a sanitizer – and therefore provides no protection against bacteria and viruses.

Which pool shock is right for my pool?

You can use cal hypo to shock most pools. But if you have hard water and calcium hardness levels are high, you should use sodium dichlor or non-chlorine shock. Every pound of cal hypo adds 5-7 ppm to calcium hardness levels. It is better to use non-chlorine shock for vinyl pools because it doesn’t fade the liners or cloudy the water, and you don’t get a dusty residue. If your pool has increasing cyanuric acid levels, you should avoid dichlor shock because every pound adds some amount of cyanuric acid.

When and How to Shock Your Pool – What You Need to Know

Now that you know what pool shock is and which type you need to use, here is what you need to know about shocking your pool, courtesy of In the Swim:

To get rid of algae – Whether the algae is green, yellow, pink or black, the best algaecide is chlorine, and lots of it. Be sure that the pH is adjusted to 7.1-7.3 range, so the chlorine shock is most potent. Depending on the severity of the algae, 10-30 ppm is needed to kill active algae blooms.

To remove bacteria and swimmer waste – Bacteria can enter the pool from many sources, most of it harmless. However, pathogenic bacteria may also exist. Use chlorine shock to remove bacteria after heavy pool use, heavy storms or swimmer ‘accidents.’ Swimmer waste includes skin, hair, lotions, cosmetics and soaps, as well as sweat, urine, feces and fungus.

To neutralize chloramines, contaminants, and cloudy water – Combined chlorine molecules are responsible for ‘red-eye’ and a strong chlorine smell. When chloramine levels exceed 0.5 ppm (TC-FC=CC), add enough chlorine or non-chlorine shock to break apart the combined chlorine, usually 10-20x the tested CC level.

You also need to shock your pool after heavy rains. The rain itself is pure water, but by the time it reaches your pool, it collects numerous airborne particles. It can bring with it dust, air pollutants, algae spores and pollen that can disturb your pool water chemistry, consume your chlorine and discolor your water. Also, heavy storms bring with it parts of overhanging trees and overflowing planters – as well as soil from the adjoining lawn laden with bacteria, phosphates and other debris.

How to shock your pool

Always check the pH level of your pool before shocking it; adjust if needed. Make sure the pH level of your pool is between 7.1-7.3.

Other tips include:

  • Clean your pool – remove debris, leaves and the pool cleaner.
  • Try to gauge how much shock your pool needs.
  • Add shock to your pool directly. If you have a vinyl pool, make sure you pre-dissolve chlorine shock.
  • Shock your pool at night, as sunlight quickly burns off chlorine.
  • To circulate and distribute the shock properly, make sure you run the filter and brush your pool.

Here are some handy pool shocking tips that can help keep your water safe:

Do not shock your pool through your skimmer – When calcium hypochlorite or dichlor pool shock combines with chlorine, it releases a deadly gas. If you add pool shock through your skimmer, it can create this gas in a small space, causing your filter system to explode.

The Take-Home Message

Shocking your pool can keep your pool water safe and clean. But when it comes to pool maintenance, there is another issue that you need to be careful about: pool leaks.

Finding a leak in your swimming pool can be a difficult job. Some leaks are easy to locate, but there are many that pool owners can’t detect without professional assistance. Certified Leak Detection uses technology and techniques we have developed over 20 years in business. In addition to quick detection and repair of swimming pool leaks, we provide industry-leading leak detection and repair for spas and hot tubs, as well as slabs and foundations. Serving areas throughout Central Florida – including Orlando, Longwood, Lake Mary, Sanford, Kissimmee, Clermont and Winter Springs – our team is ready to answer your call.

Contact us for quick, reliable service.

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