Adding muriatic acid to above ground w/ vinyl liner

Jun 27, 2012
5
#1
I just had a water delivery to fill my pool about 3 days ago and my test kit came in the mail yesterday so I went ahead and tested the water.

I have a 24ft x 52" 14,400 gallon pool. My results are as follows:

FC tested 0
PH Tested 8
TA Tested 360
CH Tested 260
CYA Tested over 30

So I have been reading a bunch of mixed approaches on the proper way to do this and poolcalculator says to first lower the PH with muriatic acid.

Some people are saying to pour the acid in directly in front of the return, some people are saying to first dilute it in a bucket and pour it across the pool and some people are saying either way, the acid will eat through my liner. Can anyone shed some light on the correct approach!

Thank you in advance!
 

aa62579

Well-known member
May 24, 2011
409
North Central Texas
#2
I have a 18' x 48" Intex Easy Set. My TA starts out at 325, so we are in a similar predicament. I always add my MA in front of a return, pouring slowly. After I have added all of it, I swish my measuring cup around in the water to further mix things around a bit. I'm on my second year of adding acid 1-2 times per week and my pool is still fine. Diluting it in a bucket first just means you have to handle it more and that is a negative to me. If you do insist on doing it that way, make sure you add acid to water and not water to acid. When you are trying to figure out how much MA to add, make sure you put your TA figure in the pool calculator - it will make a difference.

Also, I noticed you said this was fill water, but you showed a CYA level. Fill water should not have had any CYA in it, so I wouldn't test those results unless you have added CYA.

Need to get some chlorine in there fast.
 

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
22,816
SouthWest Alabama
#3
Welcome to TFP.

The best way is to pour it in front of a running return. It will mix very quickly that way. It will not harm your liner doing it that way.

I don't know where you read that it will eat through your liner, but that surely wasn't here.

Like Allison said, fill water doesn't have CYA unless you added it. Did you add any?

Get some FC in there and start adjusting your pH.

P.S. Your pool holds a touch less than 13,000 gallons of water.
 

Suziqzer

TFP Expert
Sep 21, 2009
914
Greentown, IN
#4
I try and hold my breath while I measure and put MA in the pool... in front of the return. I wouldn't want to take the time handle it even longer to dilute it in water first. I just hold it a bit away from the edge of the pool and my return is aimed to flow a bit away from the liner anyway.

Shouldn't cause any harm to your liner and once you've had a whiff of the stuff... you won't want to mess with diluting either :)
 

Mona

LifeTime Supporter
May 23, 2007
91
SE Minnesota
#5
I dilute it. Only because I'm afraid of splashing it if I try to pour directly in the pool. I'm not the most graceful an I can pour into a bucket of water that's lower than my waist better than pouring from the jug above my waist (I'm short) into the pool.
 
Jun 27, 2012
5
#6
Thanks guys...I'll go with adding it directly into the pool in front of the return. I did not add any cya, I guess did the test wrong, really dont know too much but every little bit helps!

I purchased smart muriatic acid from home depot, but it seems like it may be "watered down" with 90 % less fumes. There's no percentage on the bottle so I am guessing it's low! Anyone have any idea before I return it.

Also is there a limit to how much I put in the pool at a time!?

Thanks!
 

wetchem

Well-known member
#7
cammo said:
I purchased smart muriatic acid from home depot, but it seems like it may be "watered down" with 90 % less fumes. There's no percentage on the bottle so I am guessing it's low! Anyone have any idea before I return it.

Also is there a limit to how much I put in the pool at a time!?

Thanks!
Is this the stuff: http://www.homedepot.com/buy/smart/case-of-2-gallons-muriatic-acid-97393.html The MSDS from that page says that it's 31.45% (20°Baume) HCl and water.

Unless someone in better know than I says otherwise, it should be good to use.

As for the amount... do you mean the largest that you can add in a single dose?

-wc
 

techguy

TFP Expert
LifeTime Supporter
Jul 21, 2010
2,697
Antelope, CA
#8
I noticed my HD had two kinds of MA

This is the 20 baume/31.45%


and this one that is 14.5% IIRC


As you can see, they were almost the same price. Also, the stock was mixed on the two pallets and someone decided they only wanted one bottle. I wonder how that went over at the register.
 

aa62579

Well-known member
May 24, 2011
409
North Central Texas
#12
You need to use the pool calculator, making sure your gallons and TA are plugged in and only add the amount needed to lower from your current pH to 7.2. You don't want your pH to fall below 7.0. Don't add anymore acid until your pH is back above 7.6 - 7.8.

Adding acid must be done in small additions, not all at once, and your pH and TA dictate how much you can add at once.
 

wetchem

Well-known member
#14
Reading thru the MSDS and other documents... this appears to be just a more dilute, less than 25%, muriatic acid; however, there isn't a specific concentration given in the documents so you'd be guessing a little-bit on the addition. The poolcalculator :scratch: - Poolcalculator.com doesn't have this concentration so I'd select the closest, 18°Baume... figure you'll need slightly more than calculated. However, IMHO, it is better to under-add than to over-add with acid... otherwise you're looking at kids/air/bakeing soda or borax

As for a single amount added... if you're not going to pre-dilute, then, personally, I'd only add a cup or two at a time slowly poured directly in-front of a return jet fairly close to the water surface, (more for control - my hands don't always like to work, than for anything else - personally, I pre-dilute as I have a small pool - fun to watch the chemicals swirl in the jet return but maybe not so much...), wait for about 15 minutes and then add more till you've added what the people here (aka poolcalc) suggest and then wait for the pool to mix and retest pH.

In any case:
- A good pair of chemical gloves is a CHEAP investment in your hands: $10 versus at least $100 in the doc's office (or more in the ER!). One example http://www.menards.com/main/housewa...-natl-rubber-glove-large/p-1393558-c-7083.htm I prefer a pair that goes about halfway up my arms. Ones that stop at the wrist or slightly thereafter, imho, don't provide enough protection.

- :!: Always add Acid to Water (think alphabet... A before W) - This Is For Safety! Should you get splashed, more than likely it will be water (best case or at worse diluted acid) on your skin. This is a good rule to follow for any chemical addition.... chemical to water.

- :!: Do not add bleach/liquid chlorine/calhypo, "by hand" at the same time you are adding acid or shortly thereafter (before).... let things mix for 1/2 hour.

- Do not add this thru the skimmer/pump! Here in the lab we've special dosing/metering pumps and they take quite the beating when working with strong acids - even after we've diluted them by 1/2 or more :!:

- Stay out of the fumes.

-wc
 

wetchem

Well-known member
#16
cammo said:
Being that I just filled thr pool, should I put the stabilizer in first before adjusting
I would adjust your pH first.
Given that you’ve just filled your pool… more than likely you’ll need to go thru the shock process. Once you get your FC above 10 the pH test in the kit will not give you a usable number. In-fact, during shock process, worry only about the FC and CC tests until someone here asks about the other tests or you have passed the conditions for shocking the pool. Save your other chemicals for when you’re in the maintain mode.
Have you gone thru the poolschool stuff yet? If not, I highly recommend taking a few hours and reading thru the information.
I’d start with: Definitions and Abbreviations
I'm sure someone will send you here so:Shock Your Pool
-wc
 
Jun 27, 2012
5
#18
so I added a gallon of muriatic acid (31.45% 20 baume) to my pool last night and it dropped the ph from 8 down to 7.2. It dropped my alkalinity from 360 to 270 - so then I my guess is now I have to raise the PH back up, then add more acid, which will bring the TA back down some more?
 

aa62579

Well-known member
May 24, 2011
409
North Central Texas
#19
With an above ground pool, high TA doesn't need to be a major concern until all your other numbers are good and you basically get bored. Instead, focus on the pH part. When it gets high, add acid.
 

Bama Rambler

Mod Squad
TFP Expert
LifeTime Supporter
Jun 22, 2009
22,816
SouthWest Alabama
#20
As Allison said, don't worry about powering the TA unless the pH rise gets really annoying. Just add acid to bring the pH to about 7.2 whenever the pH gets up to about 7.6 or so and it'll work the TA down slowly.