Stubborn pH just won't come down!

[AZPoolDad]

I've read through all the old posts on this subject, and I know the answer will probably be "just keep adding acid and the pH WILL come down eventually."

Current levels (Taylor K-2006 with freshly purchased pH drops):

TC = 7
FC = 7
pH = 8.3
TA = 110
CYA = 40
CH = 250
Water Temp = 90

My tap water has a pH of about 7.5 (I'm in Phoenix, AZ so my auto-leveller adds tap water on a regular basis due to evaporation). Past six months the pH has really wanted to settle on the high side towards 8.0. But lately I have not been able to get it to come down from 8.0+ readings. I am using fresh HASA acid and I've added two gallons (four days ago and again last night, about 12 hours ago) in the last week and the pH is not budging.

I needed to go buy some bleach and acid at the pool store, so I let them test the water. They came up with similar results as the above, but they also check for Total Adjusted Alkalinity, and said because it was "80" I need to raise my TA. I told them I wasn't interested in the adjusted level because I use the CSI and not the old LSI index. I don't think I need to raise my TA.

How many gallons of acid do I keep adding before I say "something else is up here?" It just seems weird to keep adding huge amounts of acid and not seeing the color budge (in fact, this morning's test almost led me to believe it actually went up slightly). The pool calculator tells me I only should have to add about quarter to half gallon of acid to go from 8.3 to 7.5.

Finally, I don't have new plaster. It is a pebbletec finish that was done over 10 years ago.

Any suggestions would be be much appreciated!

 

[JasonLion]

Remember that the PH test will read anything above 8.2 as 8.2, so there is no telling what your PH started out as.

Just keep adding acid. Remember not to add too much at once. Eventually you will get it down into the recommended range, and you don't want to accidentally overshoot and have to raise the PH. In 15,000 gallons I wouldn't add more than a quart of acid at a time. You can retest and add more acid as often as every half hour.

 

[AZPoolDad]

Okay, I will keep adding a quart at a time and retesting. What stumps me is that if my pH is really above 8.2, and adding a gallon should drop my pH by up to 2 points, then math would dictate that my true pH is 10.0 or above if 2 gallons didn't make a budge. I find that level hard to believe but I guess it is possible.

 

[woodyp]

Yes...it's possible.

 

[JamesW]

The 2006 has an acid demand test. See what that shows.

What does the acid label show for ingredient percentages?

What was your TA before adding the acid? If the TA is not coming down, then the acid is not good.

What is the TA of the fill water?

2 gallons of full strength acid would lower your TA by 65 ppm. That would put your previous TA at about 175. Does that sound right?

Are you getting scale?

 

[AZPoolDad]

Okay, this is the part of the show where everyone on TFP can have a good laugh at the expense of AZPoolDad. I followed JamesW's advice and went out to my recycling bin to check the percentage of acid in the gallon jugs. You know, the two gallon jugs of acid that are really gallon jugs of chlorine. I had forgotten that before vacation I bought a two-pack of chlorine because my normal HASA four-pack was unavailable with the pool store being closed. Blah blah blah, yada, yada, yada.

My acid demand test revealed four drops to get it from 8.0+ to 7.5, and at 12,000 gallons of pool water, than means about a quart will get me back in business this afternoon. Doh!

 

[JamesW]

Don't feel bad. Mistakes happen. It's just good to know that you're back on the right track.