Strange Results of TA Test (Spa Alkalinity)

by William Pike
(Virginia Beach VA, USA)

I had a strange thing happen today, when I checked chemicals first thing this morning.

I had a very low pH on my spa (Bromine at 6.0 pH at 7.0) so as I usually do I checked the TA and these are the results.

First I used a couple drops of Reagent 0007 to kill the bromine, then 5 drops of 0008 (water should turn green) it turned a real nice shade of baby blue?? so...

I went ahead and started with the 0009 sulfuric acid, after 2 drops the water turned canary yellow, not the yellow that you get with low pH but a very vibrant yellow... Have you ever heard of this happning? I've seen lots of strange reading but never this one.

I went ahead and added the proper amount of soda ash to bring up the pH to the proper level. I let it go for a few hours, when I re-checked it the Bromine was still at 6.0 and the pH level was now at 7.4. I re-ran the TA test (alkalinity measurement) and this time got somewhat normal readings, TA was low (30) but at least the readings made sense.

Thanks for the question Bill and glad to hear from you again

There are a couple of things that have happened to me over the years, and just recently at the Y.

We get our Reagents by the pint because we go through them so quickly. A pint of chlorine R-0871 brown bottle lasts about one month. I went through a pint per month when I did pools in Arizona as well.

I mistakenly put the R-0009 sulfuric acid in the hardness reagent R-0012 (they're both clear) which messed up the entire reading for the calcium hardness. That could be one problem.

Also, Reagents have a good shelf life, about 1 year if they're kept covered, out of the sun, and in a cool dry place, but they do lose their effectiveness. Be sure they're not stale.

If you got a strange reading the first time, then re-tested and got a good reading, it might have been as simple as human error. I would re-test the hot tub alkalinity a third time so you'll have a base to follow. If the alkalinity shows up 30ppm again you'll know that a simple mistake was done the first time.

If a bad reading or wrong color shows up the third time and you're absolutely sure that you used the correct Reagents, then the Reagents are probably bad.

I would advise you to get new bottles of the R-0007, 0008, and 0009 because you may not know which bottle is bad.

I know that pool and hot tub water can be tricky, but strange things like what you described normally just don't "happen". There's usually an outside source.

I'm sure you'll get it right. You probably already have by the time you get this answer.

Have fun and good luck with the hot tub


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