How Much Chlorine to Shock a Pool Calculator

Pool Shock Dosage Calculator

Cal-Hypo (65%) – Granular Liquid Chlorine (12.5%) Dichlor (56%) – Granular Cal-Hypo (73%) – Granular

Recommended Dosage:

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How Much Chlorine is Needed to Shock a Pool?

Maintaining a clean and safe swimming environment requires periodic "shocking." Shocking is the process of adding a large dose of oxidizing chemicals (usually chlorine) to the water to destroy organic contaminants, break down chloramines, and kill algae. To get the best results, you must calculate the exact amount of product needed based on your pool's total volume and the specific type of chlorine you are using.

Step-by-Step Shock Calculation Guide

1. Determine Pool Volume: Knowing your pool's total capacity in gallons is the most critical step. A standard 15,000-gallon pool requires much less product than a 30,000-gallon pool.
2. Test Current Chlorine Levels: Use a high-quality test kit to find your current Free Chlorine (FC). If you have visible algae or a high chloramine smell, you likely need to aim for a "Breakpoint Chlorination" level, typically 10 to 30 ppm.
3. Choose Your Product: Different products have different concentrations. For example, Cal-Hypo (65%) is a popular granular choice, while Liquid Chlorine (12.5%) is preferred for its fast action and lack of calcium buildup.
4. Apply the Math: Subtract your current FC from your target FC to find the required increase. Then, apply the dosage rate specific to your product.

Shock Product Dosage Rates

While formulas vary slightly by manufacturer, the standard industry averages for raising Free Chlorine by 1 ppm in 10,000 gallons of water are:

• Calcium Hypochlorite (65%): 2.0 ounces (by weight)
• Liquid Chlorine (12.5%): 10.7 fluid ounces
• Sodium Dichlor (56%): 2.4 ounces (by weight)
• Calcium Hypochlorite (73%): 1.8 ounces (by weight)

Example Calculation

Imagine you have a 20,000-gallon pool with a current chlorine level of 1 ppm, and you want to reach 11 ppm (a 10 ppm increase) using 12.5% liquid chlorine.

Required Increase: 11 – 1 = 10 ppm
Dosage: 10.7 fl oz (per 10k gal) × 2 (for 20k gal) × 10 (ppm increase) = 214 fl oz (approx 1.67 gallons).

Safety Tips for Shocking Your Pool

Always add shock to the water, not water to the shock. If using granular shock, it is best to pre-dissolve it in a bucket of pool water before pouring it around the perimeter of the pool. Always perform shocking after the sun has gone down, as UV rays will quickly burn off the high concentration of chlorine before it can do its job. Keep the pool pump running for at least 8-12 hours after treatment.