Acid demand test? CYA content percentage?

Uncle Ben

Well-known member
Apr 20, 2010
83
Southern California
What is the acid demand test for?

Is CYA generally the same concentration percentage across the board? I noticed that there is not a selection for the stregth in the pool calculator.
The stabilizer I got at Lowes said 16%

Thanks.
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
The acid demand test lets you determine how much acid would be required to lower pH by a certain amount. It isn't necessary if you use the pool calculator and fill in values for TA and Borates. The Base demand test does the same thing for raising pH.

I believe that the pool calculator assumes 100% CYA. You would have to use 6x as much of the 16% stuff.
 

Uncle Ben

Well-known member
Apr 20, 2010
83
Southern California
Thanks. Another question: what is the best way to decide what you want your FC level to be? I'm familiar with the CL/CYA chart, and I was planning on 5CL/40CYA, but then I started to wonder whether I should keep the CL to 3 or 4 since my young daughter likes to drink her bath water, so I'm sure she'll drink the pool water too.
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
How expensive was the 16% CYA? Maybe your better off returning it and getting some 100% somewhere else. I ordered some from eBay recently, and there is always walmart or *shudder* the pool store.

As far as FC goes, my understanding is that if you want properly sanitized water you never want the FC to fall below the minimum for the CYA level. This means that you have to add enough so that you FC is still over the minimum the next time you test.

I am not sure what is more unhealthy; a few extra ppm of FC or water that isn't properly sanitized. Maybe one of the experts can weigh in.
 

Uncle Ben

Well-known member
Apr 20, 2010
83
Southern California
I see your point. I understand the relationship between the two, but I guess I just don't know what the benefit is to go with a higher CYA/CL level, compared to lower levels that are still in good range of one another.

As far as the stabilizer I bought, it was around $16 I think, and was a liter sized bottle. I'll check again to make sure I'm correct about the 16% that I'm remembering.
 

frustratedpoolmom

TFP Expert
LifeTime Supporter
In The Industry
May 20, 2007
12,179
SWSuburban Chicago, IL
I don't think it can be 16% that doesn't sound right...

There is a thread floating around that explains the equivalent chlorination with drinking water and pool water with CYA - I'll see if I can find it...
 

PaulR

LifeTime Supporter
Jan 11, 2009
1,966
Cupertino, CA
The acid demand test can be useful in extreme situations, say if your pH is too high for the pH test to measure it properly. I remember one or two people who liked using it, because they had learned to calibrate drops of acid-demand reagent to amounts of acid in the pool. But the pool calculator works in nearly all situations.
--paulr
 

Uncle Ben

Well-known member
Apr 20, 2010
83
Southern California
Sorry for the confusion. I checked the CYA again and it is 99%. I was thinking of the liquid muriatic acid that I bought, which is about 14-16%.

I added about 132oz of 6% bleach, which is too much for the CYA level that I will keep, but on the CYA bottle it says that the filter must be clean before you add CYA, and I did not have the time to do the full DE filter cleaning yet (read the article about that), so I know I will lose a lot of my chlorine level to the sun before I can clean the filter and get the CYA in there. (the pool/filter has sat dormant since at least Nov 2009 and looked pretty nasty when I opened it up, but it is only at 15psi, which I think is in the normal range.

The directions also said to pour the CYA powder right into the skimmer, but I learned on TFP that most people put it in a sock/stocking and hang it in front of the skimmer so it can dissolve slowly.

One more question: directions say to not add muriatic acid and bleach at the same time, but how long do I have to wait between adding one or the other? (TA was about 140 and pH was about 8.0)
 

svenpup

LifeTime Supporter
Nov 18, 2009
835
Sacramento, CA
Uncle Ben said:
...on the CYA bottle it says that the filter must be clean before you add CYA...
This is important if you add it to the skimmer...if you add CYA to the skimmer much of it gets caught up in the filter until it dissolves so if you backwash you lose some the CYA you just added. If you added it via the sock in front of the return method you should be fine.


Uncle Ben said:
...One more question: directions say to not add muriatic acid and bleach at the same time, but how long do I have to wait between adding one or the other?...
1/2 hour is fine with the pump running (you should always have the pump running when adding chemicals)
 

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