TA crept back up after 3 weeks, should I correct it?

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watson524

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Nov 13, 2014
182
Lake Ariel, PA
On 7/18 we took the TA down to 50 with MA before we added the 50ppm borates with boric acid. 7/26 test had TA at 50, 8/2 test had TA at 50. All that time, pH was 7.4. We haven't been in it as much recently due to other issues going on but the pH seems stable.

Today when my husband tested, the pH was still 7.4 but the TA is up to 80.

Should I put in acid to get it back down to 50? I guess I thought that it would stay at 50 longer since we're using bleach for the FC.

I do need to use dichlor now to get the CYA back up since it's been since 7/18 that I've used it and based on another thread trying to figure out why my FC use is so high, I want to get it back up to 35 - 40.

I'm thinking since I'm going to use some dichlor to add about 8ppm CYA (it's below 30, I just can't tell how much below but it shouldn't be too much lower), the dichlor being net acidic should help drive TA Down and I don't need to use MA?

thanks!
 
Ok so we threw in 1.2oz of Spa 56 (dichlor) and ran a cycle. Interestingly, Spa 56 gives us higher than expected +FC and bleach gives us lower than expected +FC so we are keeping good notes.

Anyway, FC is now 14.6ppm (so we won't be getting in for a while lol!) but CYA I'm calling 37, it's less than 40 but about a quarter of the way between 40 and 30 so I'm going to say 37 and move on. pH solid at 7.4 and TA came down to 60 so I'm leaving it there and moving on.

Finally think I'm getting the hang of this. Now if we don't go in it tonite, I'll be able to do the overnite loss test with the proper CYA to see if that causes less loss (if that's not redundant LOL!)
 
Strange for the TA to rise so much over 3 weeks. Even if the bleach brand you were using had more excess lye in it, then adding acid to keep the pH in check would have lowered the TA. Did you have evaporation and then refilled the spa back up with fill water that would increase TA? Don't forget that TA needs to be compared/measured at the same pH. When the pH is higher, the TA will be higher as well, though not by a large amount.
 
Make sure you don't have static electricity on your dropper tip and that the drops are well-formed and not squirting out. Wipe the dropper tip with a damp cloth to be sure. It is very strange to have a rise in TA of 30 ppm in 3 weeks with no chemical additions to explain it.
 
Between you and me (and millions of others on the interwebs), I was wondering if the 80 wasn't a testing error.... I normally do the testing, this week my husband did it. Tho with adding the dichlor, would you expect to see it go from 80 to 60 or is that too much of a drop for only 1.2oz of dichlor? I did the second test myself and got the 60 which would mean it raised 10ppm over 3 weeks and the dichlor had no affect.
 
1.2 ounces of Dichlor in 500 gallons after that chlorine got used/consumed would lower the TA by only 3.5 ppm (right after it's addition the TA would rise by 3.5 ppm but as the chlorine got used/consumed it would drop by 7 ppm to end up 3.5 ppm lower than you started). So most likely the TA didn't rise much at all over the 3 weeks and the 50 ppm and 60 ppm are within the +/- 1 drop so 10 ppm test error. Or perhaps you tested the TA soon after the Dichlor addition and before the chlorine got used/consumed in which case it had gone up 3.5 ppm but again is within the +/- 10 ppm error of the test.
 
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