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Pool shock calculator
The right shock level depends on your stabilizer. Cyanuric acid holds chlorine in reserve, so a pool at 60 ppm CYA needs much more chlorine to shock than one at 20 ppm.
Shock for a 10 ppm dose
| Pool size | Cal-hypo 65% | Liquid 10% | Dichlor |
|---|---|---|---|
| 5,000 gal | 10 oz | 2 qt (64 fl oz) | 12 oz |
| 10,000 gal | 1.3 lb | 1 gal (128 fl oz) | 1.5 lb |
| 15,000 gal | 1.9 lb | 1.5 gal (192 fl oz) | 2.2 lb |
| 20,000 gal | 2.6 lb | 2 gal (256 fl oz) | 3 lb |
| 30,000 gal | 3.9 lb | 3 gal (384 fl oz) | 4.5 lb |
A pound of 65% cal-hypo adds about 7.8 ppm to 10,000 gallons, which is why bags often say "1 lb per 10,000 gallons".
How the shock level is set
This calculator aims for 10 ppm, or 40% of your CYA if that is higher. The 40% figure is the rule of thumb from the Trouble Free Pool community for clearing algae. It is not an official standard, so treat it as a practical guide.
Dichlor and trichlor add stabilizer each time, about 0.9 and 0.6 ppm of CYA for each 1 ppm of chlorine. Repeated shocking with them is how pools end up with too much CYA. Choose cal-hypo or liquid chlorine if your CYA is already high.
Add chemicals to water, never water to chemicals, one at a time, with the pump running. Wear gloves and eye protection, and never mix products.