Can some sources of liquid chlorine raise TA?

[hank59]

First I'd like to say Thank You to everyone in this forum. This is my first year with a pool, and thanks to the BBB method it's been clear and algae free all summer. My question is, can some sources of liquid chlorine cause TA to rise? I read this on another thread, due to lye in the chlorine. I started the season using pucks and my levels didn't move much. I know tri-chlor lowers PH and TA, which I adjusted accordingly and LQ raises PH until it burns off then it comes back down, which is exactly what happened. Beginning in July I started using 12.5% LQ I got at BJ's in gallon bottles, and my TA rose 20ppm in a week. I brought it down with acid and aeration. Then I found a place that sells 12.5%LQ in 5ga.carboys, fresh deliveries everyday. After using this LQ my TA didn't move at all for over a month. Last week I started using the leftover LQ I still had from BJ's and the TA rose 20ppm again within a week. The levels are still within range but I'm curious, could that be cause of why this is happening? Thanks.

FC 5
PH 7.4
TA 110 up from 90 last week, (read on another thread to keep TA on the low end, it slows PH rise when using LQ)
CYA 40
CH 150

 

[linen]

Bleach/liquid chlorine will not raise TA. Do you know what your fill water TA is? Have you been adding a lot lately? Do you have an autofill?

 

[Bama Rambler]

That's not normal unless it's not plain bleach. If it has any additives it's possible that they could raise the TA. Especially if it has a lot of excess lye I guess.

 

[linen]

Especially if it has a lot of excess lye I guess.

Good point bama, I forgot about the lye.

 

[chem geek]

Yes, different brands of bleach and chlorinating liquid have different amounts of excess lye in them. Those with higher amounts of excess lye will result in a greater pH and TA rise even accounting for chlorine usage/consumption. However, for the TA to rise by 20 ppm assuming you added 14 ppm FC cumulatively through the week of 12.5% chlorinating liquid, then that would require enough excess lye to have the pH shoot to 8.9 and would require 13% excess lye so this is very unlikely. Poor quality chlorinating liquid may have 1% excess lye instead of 0.25%.

Since it sounds like the TA rose and not the pH substantially, then there may have been sodium bicarbonate (baking soda) in the chlorinating liquid, but I've never heard of that.

 

[hank59]

When I first filled the pool the TA tested 60ppm so I needed to raise it. I've never added any water, only needed to drain a couple of times due to rain. Even then, it lowered the PH and the TA, but only slightly. Hasn't really rained here for a while now. The stuff I got from BJ's was Austins 12.5% pool shock. Thought it was more than a coincidence that it happened twice when using one source and it was fine for over a month with the other. I still need to buy some more CL, so I guess I'll fill the carboy and see what happens.