Calculate the exact amount of chlorine needed for your pool. Supports all major chlorine types. Maintain safe sanitization levels and prevent algae growth effortlessly.
Begin with an accurate pool volume, then test your current Free Chlorine (FC) the same day you dose, because chlorine drifts hourly under sunlight. Enter that current FC reading and your target. The CDC's Healthy Swimming guidance recommends keeping at least 1 ppm FC in pools at all times; most operators hold residential pools at 3–5 ppm for a comfortable safety margin against bacteria and algae. Next, choose your product: liquid chlorine (sodium hypochlorite, usually 10–12.5%), cal-hypo granules (typically 65–73% available chlorine), or dichlor (≈56%, which also adds stabilizer). Each has a different 'ppm per unit' strength, so selecting the right type matters as much as the volume. If your FC is being consumed faster than expected, that gap is your chlorine demand — caused by sunlight, bather load, organic debris, or low cyanuric acid. Test before sundown so you can dose for the overnight low and wake up to balanced water.
Method: dose = pool volume × (target FC − current FC) × a product-specific factor. For 12.5% liquid chlorine the rule of thumb is roughly 10.7 fl oz per 10,000 gallons to raise FC by 1 ppm. Worked example: a 10,000-gallon pool at 1 ppm FC, target 4 ppm, needs a 3 ppm rise: 3 × 10.7 ≈ 32 fl oz, just under a quart of 12.5% liquid chlorine. In metric, raising 50,000 liters by 1 ppm with 12.5% liquid chlorine takes about 400 mL, so a 3 ppm bump needs roughly 1.2 liters. With cal-hypo at 65%, raising 10,000 gallons by 1 ppm takes about 2 oz by weight, so a 3 ppm rise needs roughly 6 oz (≈170 g). Always confirm the percentage printed on your container, since strengths vary and a 6% household concentration needs double the volume of a 12.5% pool product.
Chlorine products are strong oxidizers and dosing accuracy protects both swimmers and equipment. Add liquid chlorine slowly in front of a running return jet so it disperses instead of bleaching one spot of liner; pour at the water surface, never splash. The single most dangerous mistake is mixing chlorine types — combining cal-hypo with liquid chlorine, or any chlorine with acid, can release toxic chlorine gas or even cause fire, so dedicate a separate clean scoop to each product and never reuse a bucket. Do not swim until FC settles back into range, generally 4 ppm or below for comfort. Retest 4–6 hours after dosing and again the next morning; if FC keeps crashing overnight, your cyanuric acid is likely too low to shield chlorine from UV. Store chlorine cool, dry, and away from any acid. When in doubt, dose conservatively and add more after retesting rather than overshooting.
Most residential pools should maintain a Free Chlorine (FC) level between 3 ppm and 5 ppm to ensure effective sanitization without irritating swimmers.
Most pools need chlorine added every 1-3 days, depending on bather load, water temperature, and sun exposure. Test two or three times a week and top up to keep Free Chlorine in range; a saltwater generator or a floating feeder can stretch this interval by dosing continuously.
Liquid chlorine (sodium hypochlorite) acts fast and adds no stabilizer, but it is weaker and has a shorter shelf life. Granular chlorine such as cal-hypo or dichlor is more concentrated and stores longer; dichlor and trichlor also add CYA, while cal-hypo adds calcium, so factor that into your water balance.
Yes, UV rays can destroy up to 90% of your chlorine in just two hours. This is why Cyanuric Acid (Stabilizer) is used to protect the chlorine from the sun.
Yes. Free Chlorine much above 5 ppm can irritate eyes and skin and, at very high levels, bleach swimwear and corrode metal fittings. If you over-chlorinate, simply leave the pool uncovered in sunlight so the UV burns it off, or use a chlorine neutralizer (sodium thiosulfate); never swim until it falls back to about 1-5 ppm.
Yes, provided it is plain and unscented. However, pool-grade liquid chlorine is typically 10-12.5% concentration, making it much more cost-effective than standard bleach.