How much shock do I add to my swimming pool?

With over 8 million residential swimming pools across the US ranging from 5 thousand gallons to over 30 thousand gallons, the amount of shock you need to treat a swimming pool isn't a one-size-fits-all answer. But it IS an easy answer to get to.

To figure out how much shock you need to put in your swimming pool, all you need to know is the total volume of your swimming pool in gallons.

How to Calculate the Total Volume of Your Pool & How Much Pool Shock You Need

Your first step is determining your pool's total gallons. You have three options:

1. Call the pool company that built your pool. They should have your dimensions and volume on hand.
2. Use the HTH™ Pool Volume Calculator. You'll need the dimensions of your pool for accuracy.
3. Calculate your pool volume yourself. The pool volume equation for a rectangular pool is: Length x Width x Average Depth x 7.5

Calculate Your Average Depth

Start by calculating your average depth: that's your shallow-end depth plus your deep-end depth divided by two. (Shallow end + Deep end) / 2 = Average Depth. For example, if your shallow end is 3 feet and your deep end is 8 feet, your average depth is 5.5 feet.

Check Your Shock Package for Dosing

Once you have your pool volume in gallons, look on the package of shock to see how many pounds or pods you need. Often times you'll find a chart right on the package.

For example, HTH™ Pool Care Shock Advanced asks for one pound per 13,500 gallons. So for a 21-thousand gallon pool, you'd want to round up to two pounds of shock. Always round up to make sure your pool gets enough chlorine.

How Do I Add Shock to My Pool?

First, you want to make sure your pool water is balanced—meaning your pool is within the correct ranges for free available chlorine, pH, alkalinity, calcium hardness, and cyanuric acid (CYA).

To make sure your pool water is balanced, test your pool water with HTH™ Pool Test Strips or an HTH™ Pool Test Kit. Dip it in the water about 18 inches down for two seconds, pull it out and don't shake off the water. You can compare it to the color panel on the side of the bottle or text a picture to 484-123 to get customized pool care instructions.

Once your pool water is balanced and good to go, it's time to add shock. Ideally, you want to wait until sundown to add shock to your swimming pool because the UV rays burn off the very chlorine you're putting into your pool. You should leave the pool uncovered overnight to allow the shock to work, and to avoid damaging the pool cover.

How to apply shock to the pool?

There are different methods for applying shock depending on the product type. The most important rule: only follow the instructions you find on your specific shock product package.

Here's the General Process

1. Put on your safety goggles and rubber gloves.
2. Check the package for application instructions—some pods and granules add directly to the pool.
3. Add your pool shock product to the pool.
4. After pouring or distributing evenly over a wide area in the deepest part of the pool, take your pool brush and disperse the granules so they don't sit in one spot.
5. Do not enter the pool until free available chlorine levels return to 1–4 ppm.

Common Questions About Pool Shock

Can I Add Algaecide and Shock at the Same Time?

No. Let the shock try to fight the algae first. Add pool algaecide about 24 hours after shock to finish the job and prevent future algae blooms.

Can I Add Too Much Pool Shock to a Swimming Pool?

It's tough to add too much shock to your swimming pool. When you're measuring the amount of shock to put in your pool, it's okay to round up. In fact—it's recommended. You'd have to put an excessive amount of shock in your pool to truly cause dangerous swimming conditions.

Swimming in a pool with an extremely high chlorine level may cause skin, hair and eye irritation. But that's why you should test your pool water regularly to make sure chlorine levels are between 1 and 4 parts per million.

Which HTH™ Pool Shock Should I Use?

HTH™ makes several shock formulations designed for different pool types and needs. Each has different concentration levels, so dosing varies by product.

• HTH™ Pool Care Shock Advanced is the most popular choice for routine weekly maintenance—it requires one pound per 13,500 gallons and works fast without adding cyanuric acid that can cause chlorine lock.
• HTH™ Pool Care Shock is the standard option for weekly treatment, requiring one bag per 12,500 gallons.
• HTH™ Pool Care Shock Ultra is a concentrated formula, using one bag per 16,750 gallons.
• HTH™ Pool Care Salt Shock is specifically designed for saltwater pools and requires one dose per 10,000 gallons.

Always check your product package for exact dosing, as formulations vary. The most important step is knowing your pool volume first, then following your specific shock's instructions exactly.

Getting the right amount of shock prevents guesswork and keeps your pool healthy. Know your volume, check your product's dosing chart (each HTH™ shock varies by formulation), and apply shock at the right time for best results.