Muriatic acid ineffective.

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sktn77a

sktn77a

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May 16, 2010
2,638
Chapel Hill, NC
OK, I've spent a couple of hours on the internet researching this one.......... Equivocal opinions (to say the least).

I'm winterizing my pool and the pH was way too high (off scale on my Taylor 2005 kit pH measure). So I went to Lowes and got some muriatic acid. Looked a little strange when I opened it - no strong HCl/Cl gas when I opened it and it looked clear instead of a greenish color. Added about 1/2 gallon (should have been WAY too much) and the next day the pH was unchanged. Checked the pH of the acid and it appeared neutral! So I took it back to Lowes. Went to a different Lowes (thinking maybe their supply was a year or so old) and got another gallon - same thing!!!??? Tested my tap water and the pH was way alkaline. Could my Taylor reagent be bad, too?

What thinketh the combined wisdom of this learned body?
 
Thanks Marty, it doesn't say the strength anywhere, but it says "for etching concrete", and is what I've always got from Lowes. Let me research this further - see if they're watering down their MA!

Edit: Found it on their website: 20° baume (31.45%), which should be fine(?)
 
Yes. That should be fine. MA does not go bad. So not sure why it is not effecting your pH.
 
Did the TA change?

Maybe the pH is really not high, but appears high due to chlorine interference.

There have been several posts recently about chlorine interference causing the pH to read purple.

Does the color go purple right away or is there a transition from normal color to purple?

When chlorine combines with phenol red, the reagent converts from phenol red to chlorophenol red, which is a different indicator with different colors.

The pH reagent has chlorine neutralizers that should neutralize chlorine up to 10 ppm.

Maybe the neutralizer in the reagent is not working correctly for some reason?

Put 1 drop of R-0007 thiosulfate in the sample and mix to neutralize the chlorine before adding the pH reagent.

Ph test color changes rapidly

Odd situation. Did pH test was 7.4, within 2-3 seconds, the color went up rapidly ending with purple. Redid test 3 times. Meter said 7.4. Water temp 56. Ideas?
www.troublefreepool.com www.troublefreepool.com

Pool PH Suddenly extremely high (maybe)?

I maintain my own chemicals and have for many years. I've never had an issue. I use a pool company for opening and closing and normally ask them not to put any chemicals in. Today they arrived to close the pool and misunderstood my request for no additional chemicals. Something they did caused...
www.troublefreepool.com www.troublefreepool.com

 
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sktn77a said:
Checked the pH of the acid and it appeared neutral!
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Checked it how?

Put a small amount of the acid in a plastic container and sprinkle in some baking soda to see if it bubbles.

It should bubble a lot from producing carbon dioxide.

Do not do this test in a sealed container because the generation of gas will create pressure.
 
Good points, James W (Chlorine interference and baking soda). I checked the timing of the crimson pH coloring and it was immediate, so I think the pH really is high. Added more of the acid(?) last night and began to get a bit of a whiff of hydrogen chloride gas towards the bottom of the bottle. Tested the alkalinity (90, down from 100) and pH (7.6, down from 8+) this morning. So it looks like that second bottle of acid had some juice in it. Still, I added 3/4 of the first quart (no effect at all) and 3/4 of the second quart before I got the pH down to a number I can live with. Ordinarily, less than a quarter of this would have been needed.

So I guess both bottles were sub par. The first one did little, if anything, and tested ~7.0 with my K-2005 kit. The second bottle tested somewhat below 7.0 but I couldn't accurately measure it (as the color scales doesn't go below 7.0).

My take home message is to avoid the "Kleen Strip" muriatic acid sold by Lowes ("90% lower fumes than standard muriatic acid and won't burn skin") in the green bottles as I don't know how a 30% solution of hydrogen chloride can gave fewer fumes, not burn skin, and still be as potent as "standard muriatic acid".
 
So looking it up for a member in the spring, it appeared Kleen Strip got shady with its MSDS. The weak ones listed ‘proprietary strength 10%-30%’ on the MSDS and nothing at all, anywhere on the jug. So they wanted people to think they were getting the strong kind when they weren’t. Look for any of the buzzwords like green, eco, no/low fumes, etc and consider those half strength. Nothing wrong with them, you just need twice as much.

It also seemed that if it was full strength, they bragged about the 31.45% on the label and made it easy to see.
 

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Yes I just learned this the hard way with Klean Strip today. Lots of concrete dust in my pool from pool deck build and my pH wasn’t coming down nearly as quickly as pool math said it should. Took about 3x as much as calculated for 31.45%. So something in the 10ish % range as phonedave suggested, and at the bottom end of what’s in the SDS.

Dan
 
Danimal92Sport said:
Lots of concrete dust in my pool from pool deck build and my pH wasn’t coming down nearly as quickly as pool math said it should.
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The concrete dust is very alkaline and it will react with and neutralize a significant amount of acid, so you can't equate the pH drop expected with no dust to a pool with a lot of alkaline dust.
 
Just as an additional point to be aware of, some concrete cleaning and etching products are formulated wtih surfactants too. Typically an ethoxylated alkylphenol, non-ionic surfactant. These aren't really nasty, but probably not something you want in your pool. SDSs are safety related documents, they're not a full formulation. They're only required to list hazardous ingredients so if you're looking at any "cleaning product" just be aware that it may have other things in it as well as the acid or base listed on the SDS.

If you're wandering around looking at etchants, you also have to be really careful not to get something designed for glazed ceramics or glass as these can be formulated with HF (hydrofluoric acid) rather than HCl. Trust me on this, you do not want to be messing around with HF and you definitely don't want it in your pool.
 
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JamesW said:
The concrete dust is very alkaline and it will react with and neutralize a significant amount of acid, so you can't equate the pH drop expected with no dust to a pool with a lot of alkaline dust.
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I wasn’t, I was just making a comment that I’m not seeing the drop in pH I’d expect from the acid.

Edit: perhaps you mean that pool math is assuming a normal pool when it recommends an acid addition but my pool is not normal with all of the concrete dust in there - good point.

Dan
 
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As far as I can tell, Kleen Strip is just weaker HCL. There is nothing in there such as surfactants or Hydrofluoric Acid (That would be a real problem)

I think the last two gallons of HCL that I bought were Kleen Strip. Maybe that is why I do not have issues storing my jug of acid around metal. Others have said that even with the lid on, a jug of acid that was left on or near a metal surface has rusted that surface in a matter of a few weeks. I have had acid in my pool shed sitting 5 inches from a metal support (and 3 feet from my lawn tractor) for 2-3 years with no rust. Maybe it is because it is a weaker concentration. If that is the case, I will take it as a win. I do not use much acid in my pool. Usually only if I am adding borates (via borax) or on some very rare occasions my pH may float up slightly.

I use it all of the time in my hot tub, but since my tub is only 330 gallons, using a lower concentration HCL is not a big issue.
 
phonedave said:
Maybe that is why I do not have issues storing my jug of acid around metal. Others have said that even with the lid on, a jug of acid that was left on or near a metal surface has rusted that surface in a matter of a few weeks.
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It’s brand specific. Specifically the vented cap that they all have and how much so it is. I stored Pool Store 31% for years with no issues, both in my garage on the tool bench and in my shed. But the only thing going for me was that flimsy cardboard gasket so even my brand could have had issues somewhere else.
 
One member earlier this year was violently shaking his to prove it was not vented. It was vented, it just didn’t leak. At best he was right. At worst he took a bath in acid. 🤦‍♂️
 

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