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Help With Dropping Ph


Venams

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Last 4 hot tub fills I had a nice system down where I could quickly get my TA down to about 50-60 and PH at 7.5 with 50ppm Borates added (3 cups Boric Acid).

Not sure if this is the problem but while brining the TA down I added the Boric Acid, which I usually add when the TA is at desired point.

My PH was lower than previous fills at about 7.0 / using the POOL CALCULATOR it stated that I Could add BORAX (which I previously had on hand) at 2.7 ounces. Added and voila PH was right at 7.5 sweet point!

Used the tub about twice since then (about 2 weeks ago) and remeasured:

TA= 60

PH=7.0

I didn't expect PH to drop back down. Is this a problem and if so how do I remedy the drop in PH?

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The pH should not drop back down unless something acidic was added to the spa. If your disinfectant level was high and dropped, then the pH could drop but not usually by that much. What are you using for your disinfectant at this point? If you are using Dichlor, then that is net acidic because chlorine usage/consumption is acidic. It's only after you switch to using bleach where the pH is stable from the bleach addition and usage/consumption combined. Most pH rise after that is from carbon dioxide outgassing which is why you keep your TA lower.

If you were using non-chlorine shock (MPS) then that is quite acidic so is another possibility.

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chem geek. I was still using Dichlor because I hadn't reached 35ppm yet. I didn't want to use my Taylor kit to test it since it takes so much of the reagent for the CYA test and the dip strips aren't very accurate.

I'm thinking that's the reason my PH dropped?

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Yes, that's probably the reason since Dichlor is net acidic when accounting for chlorine usage/consumption.

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