Trouble Lowering pH in Newly Constructed Pool

[JustAnother24]

Hi, hoping to get some help here.

Our pool company handed over maintenance to us last Friday (3/3/23), and my TF-Pro kit arrived yesterday (3/6/23). When testing my numbers came back as:
FC - 0.5ppm
pH - (very pink) above 8.2
TA - 80
CH - 175ppm
CYA - 60

Our pool is not very large (7961 gallons), and we have a spa. I used the Pool Math app to determine how much chlorine to add - I ended up doing 71oz of 10% Bleach. I waited 30m and tested this again, and FC came out to 5.5ppm (CC was 0). I then added 17oz of 20 Be (31.45%) muriatic acid, waited a couple hours and tested pH again - pH was still very high , above 8.2. I repeated this process and added the same amount (17oz), retested 4 hours later and again pH is still above 8.2

At this point, I'm wondering if I've misread something, or am doing something wrong. I'm not sure why the muriatic acid isn't lowering the pH. As for application, I slowly added the acid in front of the return jet, pump running at 100%.

My guess is I'm supposed to just keep repeating this process, adding about a water bottle worth of muriatic acid until it finally shows that it should be coming down? Any advice is appreciated - brand new pool owner and first time pool maintainer, hoping to educate myself and not screw things up. Thank you.

 

[mknauss]

Welcome to the forum. A quick check in Poolmath shows that 17 oz of MA will lower into the lower 7's. So do that until you test in the 7's. I would only do it twice or three times a day. Be sure you are circulating and brushing the pool after each acid add. Also be sure to measure TA every couple times as when you add acid, you consume alkalinity.

Be sure to read Pool Care Basics

 

[ajw22]

Welcome to TFP.

17 oz of 31% Muriatic Acid should lower pH by 0.5 and TA by 8.3 in your 8,000 gallon pool.

Add 17 oz and then retest in 15 minutes. I suspect you are lowering your pH and in four hours the curing plaster is causing the pH to rise.

 

[JustAnother24]

@ajw22 @mknauss

Okay, I just added my 3rd round of 17oz muriatic acid. I tested 15 minutes later, but again, the pH was above 8.2 (still bright pink). I also brushed after the acid was added with filter running. TA measured at 70 this time (it went from green to almost no color at 6 drops, and turned red on 7, so maybe it's actually between 60-70?).

Seeing as this is the third addition today, do I stop and begin again tomorrow?

 

[mknauss]

Seeing as this is the third addition today, do I stop and begin again tomorrow?

I would. The higher pH is not really that big of a deal as your CH is low and your TA is fine.

 

[ajw22]

Post a picture of the pH test with a white background behind it.

 

[JustAnother24]

@ajw22

As requested!

 

[mknauss]

I see that as 8.2. You have to look at the Hue, not Intensity. Use one less drop of reagent to see if you get a better match.

Test again in the morning and add the acid until you test in the 7's

 

[JustAnother24]

Update on my levels, after two more rounds of muriatic acid (17oz and 10oz).

FC - 6.5ppm
pH - still ~8.2
TA - 60
CC - 0.5ppm

 

[mknauss]

Joys of new plaster.