Problem with the T/A

[davidandbess]

Hi everyone, my friend,s pool is a little green and I told him to add 3 OR 4 of gallons of bleach and test for all the relevant results, he gave me his test results but could not get any reading for his T/A and when I went up with my test kit I could not get anything either I adhered to the correct amounts and from the green it just went to a whitish colour all with 40 drops of the reagent.
What gives with the T/A ?
His other results are as follows
fc-21
cc-1
tc-21
ph7.4
CYA-90
his pool is vinyl with 18,000 gals
Regards D/B

 

[AnnaK]

My best guess is that you don't have any TA in there to test for.

You could try this experiment: fill the TA cylinder with the required 25 ml of pool water. Add a tiny speck of baking soda. Then do the test per instructions. Go with just one drop at a time with the titrant. You'll have just a little alkalinity and won't need very many drops to effect a colour change from green to hot pink.

Please let us know if that worked.

 

[frustratedpoolmom]

My best guess is that you don't have any TA in there to test for.

You could try this experiment: fill the TA cylinder with the required 25 ml of pool water. Add a tiny speck of baking soda. Then do the test per instructions. Go with just one drop at a time with the titrant. You'll have just a little alkalinity and won't need very many drops to effect a colour change from green to hot pink.

Please let us know if that worked.

Great idea, had me stumped. He could test his tap water too, right?

 

[AnnaK]

Sure. It's always a good idea to run a full test set on the fill water and record it in the pool log.

But in this case, testing the fill water is not giving us any useful information. If the fill water has no measurable alkalinity we haven't learned anything to help us with the pool water problem. And if it does, it clearly is way too low to make any difference to the pool water.

 

[chem geek]

There's definitely TA in the water. If there wasn't, it would either be very low in pH and be red in the TA test immediately or adding just one drop would have it go from green to red as with distilled water. The Taylor K-2006 instructions state the following:

High halogen level may change indicator reaction from green/red to blue/yellow; to prevent, add thiosulfate prior to testing.

The chlorine level is high so the above interference may be happening. Perhaps it was in between green and blue to start, though I don't know how a red-yellow would be confused with white. Also, 40 drops is excessively high. Anyway, the suggestions about testing the tap water is a good one. Most tap water has some TA in it, but not usually very much unless it's well water (my tap water has a TA of around 80 ppm).

Richard

 

[frustratedpoolmom]

My tap water from Lake Michigan has a TA of 120.

 

[AnnaK]

Thank you Richard.

We use well water. Our pH is 7.5, TA is 80, no copper or iron. Thinking of bottling it