Maintaining a clean and safe swimming pool involves regular treatments, and one of the most important of these is shocking the pool. This process involves adding a high dose of chlorine or other sanitizing chemicals to kill bacteria, algae, and other contaminants. But many pool owners wonder whether they should recirculate or filter when shocking the pool. The answer depends on your specific system, the condition of the water, and the type of shock you’re using. Understanding the function of your pool’s circulation and filtration systems is essential for getting the most out of the shocking process.
Understanding the Pool Circulation and Filtration System
What is Pool Circulation?
Pool circulation refers to the movement of water through your pool’s pump and plumbing system. The primary goal is to ensure that chemicals are evenly distributed throughout the water. Proper circulation helps prevent stagnant areas where algae or bacteria can thrive and supports the overall health of your pool.
What is Pool Filtration?
Filtration is the process of physically removing debris and ptopics from your pool water using a filter system. Whether you have a sand, cartridge, or DE (diatomaceous earth) filter, the filtration system is critical for trapping contaminants and keeping the water clear. Filtration works in tandem with circulation to maintain a clean swimming environment.
What Does It Mean to Shock a Pool?
Purpose of Shocking
Shocking a pool means adding a concentrated dose of chlorine or other oxidizing agents to destroy organic waste, bacteria, and algae. It is usually done when the pool water becomes cloudy, starts to smell, or after heavy usage. Shock treatments also help eliminate chloramines, which are the byproducts of chlorine doing its job and can cause irritation and odors.
Types of Pool Shock
- Calcium Hypochlorite: High in chlorine and effective for heavy contamination.
- Sodium Dichlor: Contains stabilized chlorine and dissolves quickly.
- Potassium Monopersulfate: A non-chlorine shock used for regular maintenance.
The type of shock you use may influence whether you should use the filter or just recirculate the water.
Should You Recirculate or Filter When Shocking the Pool?
The Role of Recirculation During Shocking
When you set your pool pump to recirculate, the water bypasses the filter and moves through the system without any debris being removed. This setting is ideal if your filter is clogged or if you’ve added chemicals that don’t require immediate filtering. Recirculating is beneficial for distributing the shock evenly without overloading the filter with ptopics.
When to Use Recirculate
- Immediately after adding pool shock to help mix the chemicals thoroughly.
- When the filter is dirty or being serviced.
- If you’re using a flocculant along with the shock, which requires ptopics to settle before filtering.
The Function of Filtering During Shocking
Using the filter setting on your pool pump means the water is being pushed through the filter media, trapping dirt, debris, and ptopics. While this helps clean the pool, running the filter during shocking can sometimes lead to clogging if there’s a lot of debris present. Still, filtering can be effective in the hours after shocking to help clear the pool faster.
When to Use Filter
- After the shock has had time to circulate and react with contaminants (usually 8-12 hours later).
- When water clarity improves and larger ptopics have been broken down.
- If you’re using a non-chlorine shock that doesn’t produce heavy residue.
Step-by-Step Guide: Best Practices for Shocking Your Pool
1. Test the Water
Before shocking your pool, test the water using a test kit or strips. You want to know the current pH, chlorine levels, and presence of chloramines. The ideal pH for shocking is between 7.2 and 7.4 to ensure the chlorine works effectively.
2. Clean the Pool
Remove any large debris from the pool using a skimmer or pool net. Vacuum the bottom if needed to eliminate dirt and leaves that can react with the chlorine.
3. Choose the Right Time
Shock the pool in the evening or at night to prevent sunlight from breaking down the chlorine too quickly. UV rays can reduce the effectiveness of pool shock before it has time to do its job.
4. Set to Recirculate First
Turn your pool pump setting to recirculate for the first 2 to 4 hours after adding the shock. This ensures even distribution of chemicals throughout the pool water. It avoids forcing debris through the filter while the shock is still actively working on contaminants.
5. Monitor the Water
After a few hours of recirculation, switch to the filter setting to begin cleaning up the oxidized waste from the water. Run the filter for at least 12 to 24 hours to allow the system to remove remaining ptopics effectively.
6. Retest and Adjust
Once the filter has run for a day, test your pool water again. Adjust pH and chlorine levels as needed. If the water is still cloudy or algae is visible, you may need a second shock treatment or additional filtration.
Important Tips for Effective Pool Shocking
- Always pre-dissolve granular shock in a bucket of water to avoid bleach spots on the pool surface.
- Keep the pool pump running continuously for 24 hours after shocking.
- Do not swim until the chlorine level returns to a safe range ideally 1-3 ppm (parts per million).
- Backwash your filter if you notice a drop in pressure or visible debris accumulation.
- Use safety equipment when handling shock products, including gloves and eye protection.
Common Mistakes to Avoid
Overloading the Filter
Adding shock while the system is set to filter can overwhelm your filter media, especially if the pool is very dirty. It’s better to recirculate first, then filter later.
Not Running the Pump Long Enough
Shocking the pool isn’t a one-hour job. You need to circulate and filter long enough to let the chemicals work and to remove byproducts effectively.
Shocking During the Day
Ultraviolet light from the sun quickly degrades chlorine, especially in unstabilized forms like calcium hypochlorite. Always shock your pool after sunset for best results.
Choosing whether to recirculate or filter when shocking a pool depends on the condition of your pool water and the type of shock treatment used. For best results, begin with the recirculate setting to evenly distribute chemicals and avoid stressing the filter. After several hours, switch to the filter mode to remove contaminants effectively. By understanding how your pool’s circulation and filtration systems work together during shocking, you can maintain clear, sanitized, and safe swimming conditions all season long.