Small pool goes through acid

[Wire4money]

You now have pH of 7.2 and TA of 80. Let’s move forward from here.

Log every test and every chemical addition in PoolMath and we can all track what is happening.

Also log any fill water added to the pool.

Do you have an autofill?

Test your pH every 2-3 days and your TA every time before you add MA.

Confirm you are no longer using tabs.

Log everything and point out here when you think something is questionable.

Yes, auto fill. I was under the impression (TFL article about water quality) if I kept ph under control, TA would be ok. I guess I need to keep a better eye on it.

 

[Wire4money]

Ok, so I closely watched everything after getting my numbers perfect. All readings were taken about the same time of day. Started with the following:
Chlorine:4.0
Ph:7.3
TA:90
CH:300
CYA:60
Salt:3000

Then:
Mon Ph 7.4
Tue Ph 7.6
Wed Ph 7.9; add 30oz MA; Ph 7.3
Thu Ph 7.6
Fri Ph 7.9; TA 80

 

[mgtfp]

Everything says with low TA, I should not have high PH.

The point is that the TA indicator dye is simply a pH indicator that looks green at pH>4.5 and red at pH<4.5. The TA titration reagent is sulphuric acid. While adding the titration drops you lower the pH until it hits 4.5 and the indicator changes to red. How many drops you need shows how much the water can "resist" pH changes, i.e. it's buffering capability. If the test starts red before adding titration drops, the pH is already below 4.5.

If the pH test shows pH>8, but the TA shoes red immediately, then something doesn't add up.