Unable to reduce PH

[Lou-SADL]

I have a strange problem. The PH was on the high side so we bought some muriatic Acid 31.45% (see attached picture).

Thursday morning:
PH 8.1
FC 4.5
CC 0

From my last complete analysis:
CH 50
TA 110
CYA 55

I was very nervous about manipulating acid so I read a lot of posts on the subject and opted for no measurement. I added roughly 250 ml of MA with the pump on max. My husband added bleach later in the day. The amount of MA is based on the top area of the Pool Math page (beside my numbers and the TPF target).

Friday morning:
PH 8.2
FC 5
CC 0

So I added more MA, roughly 300-400ml. The pump is still on max.Since I had time, I retested the PH 30 minutes after the MA addition to the pool:

PH 7.8

So I added a bit more of MA, roughly 100ml then retested about 30 minutes later:

PH 7.7.

No more time before office so I added my daily dose of bleach and turn the pump to low.

Here are my numbers for this morning:
PH 7.8
FC 5.5
CC 0
CH 75
TA 110

Based on Pool math I should still add close to 300ml of MA to the pool to bring the PH down to 7.5. If I do so, I will have added a whole 1 liter of MA 31.45% to the pool.

Does this make any sense? Is something else going on here? I will wait for feedback before adding more MA to the pool.

 

[AimeeH]

Yes this makes sense. The PH test essentially can't read higher than the 8.2 reading you got. Your PH was most likely much higher. I didn't do the pool math to confirm but the fact that you have indeed achieved a reductions sounds normal if you were higher than the 8.1 which you likely were.

 

[Marlahoutex]

Also, what is the date on the MA? Perhaps it's old (does MA go bad??).

 

[Lou-SADL]

Ok, I will add the rest of the liter and retest in 30 minutes or so. I will also check if there is a date on the bottle.

What happens to the color when the PH is actually higher than 8.2? I never went above the color of the 8.2 on the K-1000 Taylor test kit. The highest I have measured is what I call 8.1 meaning close but not quite 8.2.

 

[Lou-SADL]

Ok, so I did add the rest of the bottle. It looked like I did not pour as much as I thought on the previous occasions. I have just tested the water 2.5 hours after the last addition of MA:
PH 7.5

I am right where I wanted but how come I ended adding 1 liter of MA 31.45% to go from 8.1 to 7.5? I am still very curious about the color the test would turn to if the PH was higher than 8.2? Or is the test color the same from 8.2 and more??

 

[AimeeH]

Ok, so I did add the rest of the bottle. It looked like I did not pour as much as I thought on the previous occasions. I have just tested the water 2.5 hours after the last addition of MA:
PH 7.5

I am right where I wanted but how come I ended adding 1 liter of MA 31.45% to go from 8.1 to 7.5? I am still very curious about the color the test would turn to if the PH was higher than 8.2? Or is the test color the same from 8.2 and more??

Yes......the color won't go higher

 

[ping]

The pH test is very difficult to read above 7.8. Once it hits 7.8 reduce the pH to 7.5 and you'll be fine from now on.

 

[Lou-SADL]

Good to know. I will be careful not to go above 7.8 for too long from now on. I guess adding MA will become part of my regular routine.

Thanks everyone!