lowering ph ??

This poolforum thread addresses this. If you can't get to it, this post by waterbear has the essentials:

"vinegar would cause acetates to form in the water (mostly sodium acetate and calcium acetate I would presume)...not sure what effect they might have but it probably isn't good. Muriatic acid only adds chlorides to the water, which are already there as sodium chorine and calcium chloride. Dry acid adds sulfates, which are suspected of causing problems to the plaster finish by some.

Also vinegar is a weak acid and just would not be effective."
 
In addition to what was said on the Pool Forum, acetic acid (the acid in vinegar) is an organic chemical. You can consider it to be a chemical relative of ethanol. Since much of what we try to do in a pool is to oxidize organics introduced into the water, why on earth would you intentionally add more and have something else that can consume chlorine? There are a very few organic substances that we add to the pool and pretty much the only one that we intend to keep in the pool is Cyanuric Acid (and its chlorinated derivatives). Sometimes, when we have trouble with soapy films (and are impatient), we buy enzymes, and sometimes when we have metal in the water we buy a chelating sequestrant (an organophosphate), and when we want to reduce an iron stain we use ascorbic acid, but these are exceptions.

Richard
 
Using vinigar to lower pH is an urban legend that has been around for a while. vinegar is only 5% acetic acid and will not have a major impact on pH unless you use a lot. It is also a weak acid (chemically speaking) even in glacial (concenrated) form. If you also have a SWG and use vinegar you can then dump in a bunch of cucumbers and make pickles! :poke:
 
Muriatic Acid (31.45% Hydrochloric Acid) is about 12 times more powerful an acid by volume than Vinegar (5% Acetic Acid). That is, it takes 12 times the volume of vinegar to be equivalent to a given volume of Muriatic Acid in terms of its affect on pH.

Interestingly, it doesn't matter very much that Acetic Acid is a "weak" acid because at the pH range of pools ( 7-8 ), the acetic acid is relatively "strong" in that it nearly fully contributes its hydrogen (it's pKa is 4.76). So the calculation to get the above is mostly about the difference in weight concentration (31.45% vs 5%), the difference in density (1.16 vs. 1.0), and the difference in molecular weight (36.46 vs. 60.05).

Richard
 
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