percentage of hydrochloric acid, hardware store vs. pool store

I was reviewing Ben's page on the BBB method and noticed this under "How does it work?":

"3. You raise your pH with ordinary 20 Mule Team Borax from the grocery, and lower with ordinary Muriatic Acid, from a hardware store or Home Depot/Lowes."

I don't know about other locales, but here in Phoenix the hardware stores (Lowe's specifically) sells acid with only 14% active ingredient, while Leslie's sells it with 29%. Lowe's price is 9.98 for 2 gallons, Leslie's is 11.59 for 2 gallons. So, for about 15% more, you get twice as much active ingredient. Just an FYI.

Actually, unless you are using a LOT of acid, I'd recommend getting the 15% . . . as long as it's 15% hydrochloric, and not 15% sulfuric.

31% hydrochloric (commercial muriatic acid) fumes badly, and even small leaks of fumes can cause serious damage to electrical wiring and exposed steel. That's why I recommend against storing it inside. 15% hydrochloric only fumes a little, and 10% doesn't fume. There are some long stories behind this, but trust me when I say that the savings on acid is far smaller than the potential for damage if you are careless about storing full strength muriatic.