How to Shock a Swimming Pool

Do you want to know how to shock a swimming pool? well…..

If your pool water is starting to look cloudy or unsanitary rather than crystal clear, it may be time to shock your pool. 

Pool shocking is essential to keep your water free from chloramines and reduce algae growth. Every pool owner understands the importance of preventing algae and keeping the water healthy to swim in. It not only causes your pool to look unpleasant and unwelcoming, but it can produce an odour and create a slippery surface. 

 The purpose of pool shocking is to raise the chlorine level to breakpoint chlorination and remove all the chloramines. So, essentially there is little to no bacteria in the pool and the pool or spa is safe to swim in.

What Is Pool Shocking?

Pool shocking is an important part of any pool service.

Shocking is the process of adding chlorine to your pool water in order to sanitise it. Chlorine is a standard treatment option for pool shocking. However, various non-chlorine alternatives can effectively sanitise your pool as this will still oxidise the water and destroy any bacteria.

  Shocking is an essential step in pool maintenance. It keeps your water clean and clear.

adding chemicals to your pool

What You Need

Shocking your pool requires time. The best time to start the shocking process is after dusk to prevent the sun’s UV rays from affecting the chlorine. Also when all the swimming is done for the day.

 Pool shock chemicals are great for sanitising your pool, but you want to avoid direct contact with them as this can cause chemical burns or respiratory problems. Make sure you have the following list of materials before shocking your pool:

  • bucket
  • work gloves
  • safety glasses
  • pool shock/chlorine
  • pool balancers
  • Face mask
  • pool test kits

 Using protective gear while shocking your pool keeps you safe and ensures that the entire process runs smoothly. Remember to keep chemicals separate from each other and never mix them as this is potentially catastrophic and could result in an extremely dangerous situation. Leading to hospitalisation or death.

What Type of Pool Shock Should You Use?

Not all pools require the same shock or chlorine for sanitisation. Some shock you can add directly to your pool water, while others need to be diluted first. Most pool shock require an eight-hour downtime following the application, but some may need longer.

  Knowing the differences in pool shock can help you determine which one is best for your pool. 

Calcium Hypochlorite

Pool owners have been using calcium hypochlorite, or cal hypo, to sanitise their pools for decades. Its grainy white texture allows it to dissolve in water.

 Using cal hypo requires dissolving the granular mixture in water before adding it to the pool water. Calcium hypochlorite requires eight hours to circulate throughout the pool before it is safe for swimming again. 

Dichloroisocyanuric Acid

To save time, we’ll call it dichlor acid. Dichlor acid is a stabilised chlorine solution containing isocyanuric acid. Although it is an effective pool shock mixture, creating too high cyanuric acid levels can affect the sanitisation ability of your pool water. Once this overdosing occurs then dilution or draining the pool or spa will be required.

 Dichlor is one of the easiest chlorine to use when sanitising your pool. It dissolves rapidly and only requires a small amount of time to dissolve. Remember to check the water balance after shocking, especially the cyanuric acid (stabiliser).

Sodium Hypochlorite

The most commonly used chlorine that is available in Australia. A very weak chlorine solution (12%) but still very effective. It would be best to reduce your pH to the lower end of 7.2 as this will increase the effectiveness of the sanitiser. 

You can add this directly to the pool without the need to dilute first. If you also have a salt chlorinator then you will not be adjusting the total dissolved salt which the pool requires.  

Chlorine tablets

Types of Chlorine

Understanding the different types of chlorine found in your pool can help when testing the chlorine level:

  • Free chlorine (FC) – the amount of chlorine actively sanitising your pool
  • Combined chlorine (CC) – the amount of used chlorine
  • Total chlorine (TC) – the total amount of free chlorine and combined chlorine in your pool (TC = FC + CC)

 Pool shocking will raise the free chlorine level over 10mg/l  and to breakpoint chlorination, removing bacteria and reducing the total chlorine to 0 mg/l. Use your pool test kit to measure the different chlorine levels  as this will help you determine how much chlorine shock you will need. You will of course need to calculate the volume of the pool or spa water and add the required amount of sanitiser according to the dosing rate of the chlorine that you use.

How to Shock Your Pool

Steps to Swimming Pool Shocking

1. Test the pool water

Use your tool kit to measure the pH level of your pool water. You can also use the kit to calculate the total and free chlorine. Subtracting the amount of free chlorine from the total chlorine will tell you the combined chlorine in your pool.

2. Wait until the sun goes down 

Waiting to shock your pool after dark prevents the sun’s UV rays from dissolving the fresh chlorine. Letting your shock circulate overnight means the chlorine will be more effective and after the swimming has been done for the day. 

3. Add the pool shock

It’s best to read the instructions that come with your choice of pool shock to determine how much and how to add it.  Remember that some types of shock require dilution while others do not.

Most pool shock feels like sand; however, there are some liquid options as well. Make sure you’re wearing your gloves and safety glasses to prevent contact with the pool shock. You want it to clean your pool water, not your hands! 

4. Let the pump run

Once you apply the pool shock, make sure your pump is running. The pump will disperse the chlorine around the water, destroying the bacteria.

The type of chlorine shock you use will determine how long you need the pump to run. Most chlorine shocks require an eight-hour downtime, but some may need up to 24 hours. 

5. Test the chlorine levels

Test the water in your pool for the next few days to ensure appropriate chlorine levels. Once the chlorine level reaches one to three ppm, the pool is ready for swimming! 

Shocking Salt Water Pools

It is a common misconception that saltwater pools do not need frequent shocking. Shocking your saltwater pool is just as important.

Saltwater pools use a specialised cell generator that converts salt into chlorine. You can adjust the cell settings to release more or less chlorine as needed for your water. 

Although the chlorine cell is an essential part of sanitising your saltwater pool, regular shocking is still necessary to maintain correct water balance.. 

adding salt to a pool

When Should You Shock Your Pool?

Typically, pool shocking should be a weekly routine to keep your pool water clean and safe. You should consider an extra pool shock treatment after certain events, such as:

  • A heavy rainstorm
  • A significant change in water level
  • A pool party
  • Human waste has been in the pool
  • Any heavy pool use

Without regular shocking, your pool can cause eye irritation, odour, and an overgrowth of algae. Sanitising your pool frequently keeps the water clean and healthy to swim in

To Ensure pool shocking success, call the 1Pool Care team in Western Australia on 0456-75-75-75 today!



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