Swimming Pool Chlorine

How to Shock Chlorinate Your Pool

Swimming Pool Chlorine

Shock chlorination, also known as pool shocking, is a process used to quickly elevate the chlorine levels in a swimming pool to kill bacteria, algae, and other contaminants. It’s an essential part of pool maintenance.  You should do this periodically, especially when you notice reduced water clarity, an unusual smell, or after heavy pool usage. Here’s how to shock chlorinate your pool:

1. Gather Your Supplies:

  • Pool shock treatment (calcium hypochlorite or sodium dichloride)
  • Pool test kit or test strips
  • Protective gear (gloves and safety goggles)
  • A clean plastic bucket

2. Test Your Water: Before adding shock treatment to your pool, it’s important to know your current chlorine level. Use a pool test kit or test strips to measure the free chlorine level and the total chlorine level in the pool water. Make sure they are within the recommended range for your pool.

3. Calculate the Amount of Shock: Refer to the manufacturer’s instructions on the pool shock product for dosing recommendations based on your pool’s size and current chlorine levels. The amount of shock required can vary depending on the product’s concentration.

4. Pre-Dissolve the Shock: To avoid any potential damage to your pool’s surface, pre-dissolve the shock treatment in a clean plastic bucket filled with pool water. Add the shock treatment slowly to the water in the bucket, stirring until it is fully dissolved. This step is important because adding shock directly to the pool can sometimes lead to localized bleaching or staining.

5. Distribute the Shock: In the evening or at night is the best time to shock the pool to minimize chlorine loss due to sunlight. With the pool pump running, pour the dissolved shock treatment evenly around the pool’s perimeter. Walk around the pool as you do this to ensure even distribution.

6. Brush and Circulate: After adding the shock, use a pool brush to scrub the pool walls and floor. This helps distribute the shock treatment and dislodge any contaminants clinging to surfaces. Leave the pool pump running for at least 8-12 hours to circulate the water and ensure proper mixing.

7. Retest and Balance: After allowing the pump to run for the recommended time, retest the pool water using your test kit or test strips. The chlorine levels should have increased. The free chlorine level should be back within the recommended range. If needed, you may need to add additional shock treatment.


8. Wait and Re-Test: Wait 24 hours after shocking your pool before using it again. During this time, the chlorine levels will stabilize. Re-test the water to ensure that it’s safe for swimming. When the free chlorine level is within the recommended range (typically 1-3 ppm), your pool is ready to use.

Remember to follow all safety precautions when handling pool chemicals, including wearing protective gear, handling chemicals in a well-ventilated area, and keeping chemicals out of reach of children and pets. Additionally, always follow the manufacturer’s instructions as the specific steps and dosage may vary depending on the product.


Maintain the right level of chlorine

Keeping your pool water chlorinated is essential to a healthy sparkling pool.  In our experience, most people often add or generate excessive chlorine in their pools.  This leads to more acid demand, cloudy water, rising pH, calcium spots, and clogged salt cells.  So, in the case of swimming pool chlorine, more is definitely not always better!

On the other hand, it is vital that there is sufficient chlorine in your pool water to keep it safe.  Insufficient free chlorine can make your water unsafe for swimming.  This is because the germs, algae, and bacteria will thrive in low chlorine. Importantly, the American National Standard for swimming pools suggests a minimum chlorine level of 1PPM.  We suggest you maintain 2-3ppm just in case your chlorine levels drop due to rain, heat, or other factors.

The ‘cloudy water’ page on our website also explains the relationship between pH and chlorine activity in the water. In short, high pH reduces the killing power of chlorine in your water, even if your test shows that your chlorine levels are correct! Therefore, if your pH is above 8.3 then the killing power of swimming pool chlorine is almost completely disabled. In many cases, we have cleared many of our client’s pools with constant algae problems by simply lowering the pH and not adding chlorine!

Shock Chlorination is not just adding shock

The video below offers information about the difference between combined, total, and free chlorine levels in your pool. It is a little technical in places but it is one of the most simple and best graphical explanations we’ve found.