Lowering pH with CO2

[chem geek]

So does that mean it would take about 5 oz of dry ice?

Yes, you are correct. But as your later post showed, it isn't more economical than Muriatic Acid and storage would be a bear, requiring one of those special high-efficiency thermos-type containers. Kind of interesting how the prices worked out to be similar. Thanks for doing that research.

Oh yeah, as for lowering the pool temperature, this would be pretty negligible for the amount that would be added to the pool. Dry ice is no warmer than about -109F or -79C but even if it were colder than that, the amount would hardly budge the pool temperature. One gallon of some substance that was even at absolute zero (which is impossible and is about -460F or -273C) mixed with 10,000 gallons of pool water at 80F would only lower the temperature by 0.05F or less than a tenth of a degree (assuming similar heat capacities for water and the substance, but even with a typical difference, we're still not talking about a large shift in temperature).