Muriatic vs Sulfuric acid

[gsmith]

I'm rather confused whether I should be using muriatic or sulfuric acid to lower pH on a regular basis. Searching the forums here seems to suggest that muriatic acid is preferred, as it doesn't introduce unnecessary sulfates into the water.

However, both local pool stores here in Jupiter FL strongly recommended sulfuric, saying that sulfuric acid will not lower the alkalinity, whereas muriatic will. This doesn't make much sense to me (don't all acids lower alkalinity?), and seems to run against the information I've found on this forum. Are they wrong, or is there something I'm missing?

PS This is my first post here, so please let me know if this is the wrong place to post the question.

Thanks!

 

[Casey]

Welcome gsmith. I'm pretty sure you're answer here will be to use MA. I've never heard of using sulfuric acid so I'll let someone else answer that.

Enjoy the site.

 

[JasonLion]

Welcome to TFP!

They are both dead wrong about how TA works. Adding any acid will lower TA, and adding amounts that change the PH by the same amount will also change the TA by the same amount, so there is no possible advantage there.

Sulfuric acid will add sulfates. Sulfates aren't a big deal unless you use a lot of acid, but they do build up and can eventually cause problems. Muriatic acid doesn't add anything that could ever cause a problem, and it is inexpensive, so no reason to try anything else.

 

[woodyp]

Sulfuric is a whole lot more caustic to deal with too.

 

[gsmith]

Thanks Jason, woodyp, and Casey. I've definitely forgotten a lot of whatever chemistry I once learned, but was pretty sure they were off the mark. It's good to hear I'm not crazy!

btw, the site's a great resource for pool novices like me. Thanks for running it!

 

[SwimAustin]

Sulfuric is a whole lot more caustic to deal with too.

A whole lot more! That 31% HCl is nasty enough. I actually splashed 6 mole sulfuric acid on myself and my lab partner during high school chemistry. As we rushed to the sink (which was aways turned on for this reason) I took the time to verify that, yes, oil of vitriol does actually feel slippery.

 

[whalers11]

I stumbled upon this post. I bought "non-fuming Pool Acid" from a local pool store -- it looked the same as the bottle of muriatic acid I usually buy, so I didn't notice it was actually sulfuric acid until I got home and read the ingredients on the label.

I hadn't been on there in about a year, but I should have realized when it rang up at $5 / gallon