Almost all pools need to be shocked regularly. Adding a lock of shock can clear the water by removing algae and other organic debris. However, too much shock might have adverse effects. Pool owners often wonder if there’s a shock treatment limit or if they can dump as much liquid or granular chlorine as they desire.
You can over shock a pool by adding more than three times the amount necessary to remove algae. Too much shock in the water will damage the plumbing, harm the equipment, increase the chlorine to dangerous levels, and potentially bleach the bottom of the pool. Over shocking can also cloud the water.
Throughout this article, I’ll explain what happens if you over-shock a pool, whether or not too much shock can harm the water’s chemicals, and how to know how much shock your pool needs.
What Happens if You Over Shock a Pool?
Over shocking a pool can put it in worse condition than before you added the treatment. Pool shock is made of highly concentrated chlorine. You can use liquid or granular shock. It’s much easier to go overboard with granular shock because it has up to 80% more available chlorine.
Here’s what happens if you put too much shock in a pool:
- The chlorine can damage the plumbing and unions. Chlorine is very corrosive in concentrated areas. If you have copper plumbing or corrugated plastic hoses, the shock could wear down the materials and leave holes everywhere. Always circulate the water after shocking the pool, especially if you think you added too much.
- Too much pool shock can wreck your pool equipment. Heaters and pumps are surprisingly sensitive to pool chemicals (especially chlorine). If you add too much shock to the water, it can rust and corrode the impeller, igniter, and other components in your pool equipment. You’ll have expensive repairs on your hands.
- Over shocking the water will make it too hazardous for swimming. It’s unsafe to swim in a pool if the water has more than 5ppm of chlorine. Adding too much shock can spike the chlorine well over 10ppm, making it extremely dangerous. It could cause itching, burning, and hair discoloration.
- Your pool liner could stain or corrode if there’s too much shock in the water. Vinyl and fiberglass are quite sensitive to chlorine. Too much shock will harm the liner. It could also stain or corrode old plaster coats. Always stir the shock with a brush if you think you added more than you were supposed to.
As you can see, it’s important to never go overboard on pool shock treatments. They’re reliable, strong, and incredibly effective. However, too much of any chemical is dangerous for the swimming pool. It’s always best to follow the manufacturer’s guidelines to know how much shock your pool needs.
Can Too Much Shock Make a Pool Cloudy?
Too much shock can make a pool cloudy because the dense granules take a long time to dissolve. It’s not uncommon for regular shock treatments to cloud the water for a couple of hours. Keep in mind that algae blooms die and turn the water cloudy from the shock, so you might not have added too much of the treatment.
Too much chlorine clouds the water, which means you’ll need a water clarifier. Most clarifiers stick to the filter media, preventing anything from getting through the cartridges, DE, or sand. You can also choose clarifiers that burn the cloudiness out of the water, but they’re not as reliable in my experience.
Robarb Super Blue Pool Clarifier is the top clarifier I recommend to most pool owners. A small amount of this container coats your filter, drastically increasing its micron density. Sand filters will remove as much debris as quad-DE filters, which are the best on the market. Clean the filter media after 48 hours, and your pool will be crystal clear.
New pool owners often have trouble knowing if they’re using too much or too little shock. After all, not using enough won’t do anything to the algae or cloudiness. On the other hand, too much shock can cause the aforementioned effects. For more details about choosing the correct amount of shock, read on.
How Do You Know How Much Shock to Use?
To know how much shock to use, follow these steps:
- Calculate your pool’s gallon total. Most swimming pools can be calculated by multiplying the length x width x depth x 7.5. Write this number down because you’ll need it for any chemical, pump, heater, and almost anything else you add to the swimming pool. If you have varying depths, use the average depth (deep end + shallow end divided by 2).
- Test your pool’s chlorine levels. You shouldn’t add the maximum amount of shock if you already have 2ppm to 3ppm of chlorine in the pool. On the other hand, you might need more shock than usual if you don’t have any chlorine in the water. Keep in mind that free chlorine and total chlorine aren’t the same things.
- Check the manufacturer’s label to know how much shock the pool needs. Every shock treatment has unique measurements. As nice as it’d be to give a tried-and-true estimate, I don’t want you to over shock the pool. If you can’t find measurements on the label, contact the company.
- Circulate the pump and check the chlorine levels after a few hours. Wait until the shock has enough time to mix throughout the pool. Check your pool pump’s gallons per minute (GPM) to know how long it takes for a full cycle. At the end of the cycle, test the chlorine and find out if you need to add more.
Strong, dense algae blooms can consume a lot of chlorine. The shock neutralizes the algae, but it’s used up. This process is why you have no free chlorine after shocking the water. You’ll need to circulate the water, add a clarifier, and add more shock to balance the chlorine levels. Remember that some clarifiers shouldn’t be used with shock, so check the label beforehand.
Can You Shock Your Pool Twice?
You can shock your pool twice if you’re getting rid of an algae bloom. Wait for at least four to six hours between shock treatments. Pool shock takes a few hours to fight the algae blooms, so it’s important to know how much chlorine is left after it gets rid of the algae. Never shock your pool more than twice every 24 hours.
Multiple shock treatments can help with algae removal. In fact, most algae programs recommend back-to-back shock treatments. Algae and chlorine neutralize each other, so you need to add enough shock to maintain the chlorine levels once the algae is gone. Don’t forget to remove the dead algae to get rid of the cloudiness.
Here’s what you should know about shocking your pool twice:
- Wait for a full water cycle before adding another shock treatment. Every pool pump has a labeled GPM (gallons per minute). Multiply the GPM by 60 to get the gallons per hour (GPH). If your pool cycles 9,000 gallons an hour and you have a 27,000-gallon pool, you’ll have to run it for three hours for a full water cycle.
- Always test the chlorine before shocking the pool multiple times in a row. The WWD Pool Test Kit lets you check your pool’s chlorine and pH. You can also use it for spas. This kit takes less than a minute to tell you everything you need to know when shocking the water. They also offer bigger kits with more reagents.
- Cloudiness doesn’t mean you need to shock the water. Pools get cloudy from excessive amounts of shock, dead algae, poor filtration, too much sunscreen (or lotion, deodorant, etc.), and various chemicals. You don’t have to shock the pool every time the water is cloudy. Instead, determine the source to know the next action.
- Calculate how long it’ll take for the chlorine to dissolve if you plan to swim in the pool. Use the previously mentioned GPM formula to know when you can swim, regardless of how many times you shocked the water. Pool shock can cause all sorts of side effects if it’s not completely dissolved.
Weekly or bi-weekly shock treatments should be a regular part of your pool maintenance schedule. However, you shouldn’t have to regularly shock the water more than once per week. If your pool doesn’t hold chlorine long enough, check if the cyanuric acid is between 40ppm to 90ppm. It retains chlorine through evaporation and direct sunlight.
Can You Shock a Pool Multiple Days in a Row?
You can shock a pool multiple days in a row if you want to remove algae blooms. However, it’s best to avoid shocking your pool more than once per week if there’s no algae in the water. If you keep having to add shock, you should increase the tablets, salt generation, or liquid chlorine in the water.
Shocking your pool too often can damage the equipment and liner, but you can shock it several days in a row if you need to get rid of algae. It’s important to know how often you should shock a pool; otherwise, you’ll end up wasting your time and money while creating a hazardous swimming environment.
Before shocking your pool multiple days in a row, consider these tips:
- Always test the chlorine and other chemicals before shocking the water.
- You can use a smaller dose for consecutive shock treatments if you only need to spike the chlorine levels a little bit.
- Check the clarifiers and algaecides you might add, because many of them can’t be used with shock (and the chlorine often has to be within a specific range).
- Don’t add heavy shock doses less than 24 hours before a pool party.
- Make sure your base chlorination process is providing enough chlorine (salt, tablets, liquid, etc.).
- Clean the filter if it goes higher than 25 PSI to prevent the shock from sitting in the filter and ruining the media.
How Long Does Pool Shock Take to Work?
Pool shock takes between four to six hours to work, but some treatments take up to 24 hours. If you’re removing a lot of algae from the water, you might have to add multiple treatments over the course of 48 to 72 hours. Many shock treatments can be combined with algaecides to remove and clear heavy algae blooms.
For example, Coral Seas Green to Clean uses one pound of algaecide per one pound of shock. Each pound treats up to 10,000 gallons of water. I suggest doing the treatment two days in a row. Run the pool pump the entire time for maximum circulation. Clean the filter when the process ends, and you’ll be good to go.
You can swim after shock treatments, but it’s important to wait around six to twenty-four hours, depending on the pool’s chlorine levels. Pool shock isn’t an instant treatment; it requires proper circulation, concentration, and brushing. You can make the pool shock work much quicker if you turn the pump to its highest speed and clean the filter for maximum water flow.
Do You Have to Shock a Swimming Pool?
You have to shock a swimming pool to maintain the chlorine levels. Chlorine tablets, liquid, and salt-generated chlorine aren’t enough to steady the chlorine at the recommended 2ppm to 4ppm during the summer. Add a small shock treatment in the middle of the week to remove algae and organic debris brought by swimming, pets, and nearby plants.
In the Swim’s Calcium Hypochlorite Pool Shock is one of the best you can get your hands on. It comes in a 50-pound bucket, which is more than enough for one to two pool seasons (some pool owners can get up to four pool seasons per bucket). With up to 68% available chlorine, you’ll have no problem spiking the chlorine and removing algae blooms.
It’s always better to under-shock a pool rather than over-shock it. You can add more shock, but it takes a long time to get rid of excessive amounts of the treatment.