Pool anti-freeze

[chem geek]

I agree with framcus on the toxicity discussion. However, you would have to use a very large amount of anti-freeze, or any dissolved substance for that matter, in order to significantly reduce the freezing point of a large body of water such as a pool. The freezing point depression constant for water is -1.86 C/m which means that you get a lowering of the freezing point of water of 1.86C (3.35F) degrees for every mole/kg concentration of substance in the water (it doesn't matter what the substance is -- salt would work just as well but is not in anti-freeze because salt increases conductivity which can corrode while the glycols do not).

Even an SWCG pool with 3000 ppm TDS (about 2800 ppm salt) the freezing point is only depressed by one-tenth of a degree Celsius (about two-tenths Fahrenheit). Perhaps I'm missing something, but I don't think you should use anti-freeze in your pool.

Richard