Pool anti-freeze

[Poconos]

I'd like to hear from Chemgeek on this. Proplyene glycol is the major ingredient in RV antifreeze. Significantly different from Ethylene glycol which is the green stuff used in older vehicle cooling systems. EG is sweet and animals tend to to go to it, nasty poison.
Al

[framcus]

Propylene glycol is considered by the FDA as GRAS (generally regarded as safe) and can be used in foodstuffs etc. Although drinking large amounts is not to be recommended! Ethylene glycol is poisonous to humans and animals. Propylene glycol is converted to lactic acid in the body (what your muscles produce when you perform rigorous exercise) whereas ethylene glycol is converted to oxalic acid, which is toxic and causes among other things convulsions, kidney failure and death. More information available at :
[URL="http://www.atsdr.cdc.gov/tfacts96.html"]

50% propylene glycol with water freezes at -26degrees F.

I bought a gallon today at a local hardware store for $4.50

Clearly propylene glycol is preferable for this use.

[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

[waste]

I've been waiting to type this for a while...
When you blow out the lines, water is still left in them (water clings to the pipe surfaces and will, eventually find it's lowest point and puddle there). If one does a 1/2 ***ed job of it, there is enough to fill the pipe it's in and, if the water freezes - you could burst the pipe (I seem to recall a discussion on 'lateral expansion' of ice here). The antifreeze should mix with whatever water is left in the line and provide enough protection to prevent the water from freezing and compromising the pipe. For many pool owners, who had the job done by a competant builder, it should never be a problem because the pipes should be run below the frost line, however Ma Nature can always decide to have a record breaking season.

Richard, I don't think that anyone is talking about adding 1000s of gal of propoline glycol to their pool water to prevent freezing, just to the water that will remain in the pipes... but you never know