distinguishing between pH 7.8 and pH 8.0 with K-2006 test kit

[tredos1]

Hi all,

I'm not sure if there's other folks that have this problem, but I really have a hard time telling the difference between the pH 7.8 and pH 8.0 colors on my test kit and my pool loves
to run up in this range. Current numbers are: FC 5.0, pH 7.8 or 8.0, TA 70, CH 380, CYA 40, NaCl 3400. I have found that, for my situation, it appears that if I add a drop of R-0005 the
color drops by 0.2 pretty reproducibly for my pool. I can read all the other colors fine and I was wondering if you think I can use this to tell the difference between pH 7.8 and pH 8.0.
If I add a drop of the R-0005 and it turns to the pH 7.6 color, then I know it's 7.8, if it stays that color that's hard to read, then it's at least pH 8.0, maybe more. Does anyone see a problem
with this? I've tested it a few times and it seems to work okay for a range of pH readings. I'm curious to hear your thoughts. Thanks, Tony

 

[Mike1162]

I wouldn't worry about whether it's 7.8 or 8.0. Both 7.8 or 8.0 is on the high side & you'll want to bring it down. Call it 7.9 & make your adjustment.

 

[Oly]

A lighter shade of red (more transparent?) at 7.8 and full on deep red at 8.0.
More orange hues at 7.6 and below that it becomes obvious.
When FC get to 10 its all deep red.

 

[tredos1]

So, the problem is 1) I just can't see the difference, so telling me about it doesn't help me. 2) the pool 'wants' to be at a high pH. Even since I've owned it' it has consumed massive amounts of acid to try and keep it even at pH 7.6. If I drop it to 7.4, the next day it's 7.6 and the next day it's 7.8 and then i can't tell if it goes to 8.0 or above or not. The SWG is relatively new, but it did the same thing when I was adding 1/2 gallon of bleach a day too. The rest of the numbers are about the same. LSI is fine. I know the SWG wants a lower pH, but with the LSI in a good place, I'm hoping it'll be okay, I'm running it at 50% for 12 hours a day right now and it's just about keeping up, I'm letting it slowly drop down to where I want it. Can someone address the question I was hoping to get answered? Thanks.

 

[Flying Tivo]

If you use 4 drops instead of 5 maybe it could help out.

 

[red-beard]

I gave up trying to read that. I bought a pH meter and haven't looked back TFtestkits sells one for only $16. I did not see that and bought a single decimal point Apera 20 for about $45.

 

[jark87]

If I add a drop of the R-0005 and it turns to the pH 7.6 color, then I know it's 7.8, if it stays that color that's hard to read, then it's at least pH 8.0, maybe more. Does anyone see a problem
with this?

If I’m understanding your question correctly, you are trying to determine pH based on the acid demand test. You could use the treatment table from the Taylor kit to determine how much acid to add based on the number of drops of R-0005 required to get to your target pH. You could then use the pool math app to enter either 8.0 or 7.8 as your current pH reading and the same pH target used in the drop test. Then see how much acid pool math says to add for both 8.0 and 7.8. Whichever reading matches the treatment table should indicate your pH, at least in theory. Hope that makes sense.

 

[jark87]

One other point - I was having a little difficulty determining the color match on the pH scale. I bought new bottles of R-0004 and R-0005 and my colors are much easier to distinguish now. They match the scale much more clearly. I think it was the new bottle of R-0004 that made the difference. Previous bottle was more than a year old.

 

[tredos1]

Thanks everybody. I did buy new bottles of both and still struggling. I ordered the inexpensive pH meter for cross checking. Appreciate everyone's time.

 

[Mike1162]

You might want to consider a Stenner pump to automatically inject acid.