Testing pH with high FC?

tim5055

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May 11, 2014
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Franklin, NC
I have a FC of 12 or higher always because of CYA at 100. How do I test PH if the FC level invalidates the test? Thank you.
You have to get the CYA lower, or take your chances by letting the FC drop below 10.

The best choice is to lower CYA.

Have you conducted a diluted CYA test to prove it is 100 and not some higher n7mber?
 
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Saturn94

Well-known member
Mar 11, 2015
713
Virginia
I have a FC of 12 or higher always because of CYA at 100. How do I test PH if the FC level invalidates the test? Thank you.
From Pool Doc (Ben) on another respected forum (now sadly inactive):

Mix 1/4 cup pool water with 1/4 distilled water (must be distilled water!). If FC is really high (didn’t say what would be considered really high), mix 1/4 cup pool water 1/2 cup distilled water. Test the mixture as you normally do.
 
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Beduhart

New member
Oct 7, 2019
4
Houston, Texas
You have to get the CYA lower, or take your chances by letting the FC drop below 10.

The best choice is to lower CYA.

Have you conducted a diluted CYA test to prove it is 100 and not some higher n7mber?
Yes, I did it the first time, and it was at 100, so I read the forum and did it again at 50% (50% pool water and 50% tap water) and then multiply by 2 and it was again 100.
 

tim5055

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From Pool Doc (Ben) on another respected forum (now sadly inactive):

Mix 1/4 cup pool water with 1/4 distilled water (must be distilled water!). If FC is really high (didn’t say what would be considered really high), mix 1/4 cup pool water 1/2 cup distilled water. Test the mixture as you normally do.
While I‘m sure Ben wrote that and I respect his knowledge of pools, how would that work?

Pure distilled water should have a pH of 7.0, but may not always. If you pH was 8.0 and you mixed that pool water with and equal amount of distilled water at 7.0 is the test going to read 8.0? I can’t see how it would.
 

Beduhart

New member
Oct 7, 2019
4
Houston, Texas
While I‘m sure Ben wrote that and I respect his knowledge of pools, how would that work?

Pure distilled water should have a pH of 7.0, but may not always. If you pH was 8.0 and you mixed that pool water with and equal amount of distilled water at 7.0 is the test going to read 8.0? I can’t see how it would.
I have been searching around in the forum, and I found the following old post from "ChemGeek", which says that the distilled water can be used to dilute, and it won't affect the PH reading. What do y'all think?
OMG, I feel like I am back in high school Chem class (which I almost failed!!). I don't understand the science, but I can try it with and without dilution and see what results. :)
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Donldson

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If I may ask: what downside is there to lowering the CYA?

In the time this entire conversation has been going on the CYA level could have been corrected though water exchange and operational FC levels lowered to where it is a non-issue.
 

JoyfulNoise

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May 23, 2015
16,237
Tucson, AZ
Diluting with distilled water works because distilled water has zero alkalinity to it (or very, very little alkalinity). Pool water on the other hand has a much higher TA. The alkalinity of them pool water will act as a buffer and resist pH change on the addition of the distilled water. So while you cut in half every chemical concentration, it doesn’t change the pH much at all.
Thiosulfate reduction of chlorine is a bad idea because it’s not a pH neutral reaction. So if you add R-0007, you can inadvertently cause the pH to go up or down (depends on the reaction).
 
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duraleigh

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+1 what Tim5055 and Dnldson said. Lower the CYA. Why so much complication when the simple solution is available?
 

Beduhart

New member
Oct 7, 2019
4
Houston, Texas
If I may ask: what downside is there to lowering the CYA?

In the time this entire conversation has been going on the CYA level could have been corrected though water exchange and operational FC levels lowered to where it is a non-issue.

Not so easy.
I will need to get someone to do this for me, and that means $$.

I would like to find a way to check PH with this CYA level until spring. Then I will have to get someone to help me drain/refill.

:)
 

rowiac

Well-known member
Apr 20, 2018
75
Tehama County, CA
Why not use a pH meter as someone mentioned earlier?


Mine works well and as long as I wait for the numbers to stabilize, gives me consistent readings.
 
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duraleigh

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I will need to get someone to do this for me, and that means $$.
Running your CYA at 100 means $$$, too.

Most of us here consider CYA of 100 almost unmanageable. Far better approach to get your CYA down where it belongs but that is entirely your call.
 
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tim5055

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May 11, 2014
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Not so easy.
I will need to get someone to do this for me, and that means $$.

I would like to find a way to check PH with this CYA level until spring. Then I will have to get someone to help me drain/refill.

:)
Why does someone have to do it for you?

When I took over my pool the CYA was well over 250. Like you, I had problems with pH because I had to keep my FC around 20.

Pump water out, add water back. CYA goes down.

The only $$ I spent was for the water.
 

ajw22

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Jul 21, 2013
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Northern NJ
I have been searching around in the forum, and I found the following old post from "ChemGeek", which says that the distilled water can be used to dilute, and it won't affect the PH reading. What do y'all think?
OMG, I feel like I am back in high school Chem class (which I almost failed!!). I don't understand the science, but I can try it with and without dilution and see what results. :)
View attachment 121550
Taylor Technologies does not recommend dilution of pH samples ...


When testing pH, a dilution is not the answer since the introduction of different water, likely with a different pH, will produce inaccurate results.
 

Saturn94

Well-known member
Mar 11, 2015
713
Virginia
Taylor Technologies does not recommend dilution of pH samples ...


When testing pH, a dilution is not the answer since the introduction of different water, likely with a different pH, will produce inaccurate results.
Reading that section, I believe you’ve misunderstood what it was saying. It is referring to testing pH when the sample pH is out of range of the comparator.