High PH, Alkalinty within Normal Limits...At a Loss

[AshleyAshna]

Hello all,
My wife and I had a new pool put in our backyard a year ago. The pool is a 17,000 gallon in-ground plaster pool (mini-pebble) with a cartridge filter (4 large cartridges).
I have been having a high PH in the pool since it was put in, usually about 8.2 with my Alkalinity usually sitting at 90-100. My weekly routine has been this: Since I’m going to have to add about 74 ounces of Muriatic Acid to lower the PH and I know this will also lower my Alkalinity, I start with adding 4 lbs of Baking Powder to increase the Alkalinity to 120, then add my 74 ounces of Acid to bring the PH down to 7.2 and the Alkalinity back to 90-100.
Today I did my pool test and my Alkalinity was actually at 80 and my PH was at 8.2. To this, I am not sure what to do. Honestly, I’m at a loss altogether because I have friends who live in the same relative proximity to me and they claim they rarely have to add any acid for their PH. We built our pools at the exact same time. Surely I shouldn’t have to be adding this much acid each week, week in and week out?
I’m very close to just draining the entire thing and starting fresh. Any advice? I’m not sure where to go with 80 Alkalinity and 8.2 PH. If I add the acid it’s going to lower both and the Alkalinity will be very low and then the cycle starts itself all over again.
Thanks in advance

[CarlD]

Where's your Calcium Hardness level? Are your sure it's in the 200-400 range? Do you have an SWCG as well? Or are you chlorinating with cal-hypo, calcium hypochlorite?
Also, what's your CYA (Stabilizer) level.

Try NOT raising your TA and letting it just go down, say to 60 or 70. See if your pH stabilizes.

IF you CYA is low, you can try using Tri-Chlor tabs to chlorinate. They are VERY acidic and add 6ppm of CYA for every 10ppm of FC.

[AshleyAshna]

Hi Carl,

Thanks for your response.

CH was sitting at 290 the last time I checked and that was about a month ago. My CYA has been around 60 but at one point I did accidently put too much in and it got up to 90. I did some draining and now it's sitting at 60. Would those factors make a difference?

I'm not sure what SWCG is but I do know that we have chlorine tab reserve that we put 3 inch chlorine tabs in and then use the dial to control how much we want to enter the pool (1-4 dial).

So are you saying to add the 74 ounces of muriatic acid and not do anything with the Alkalinty and just see what happens?

[CarlD]

Hi Carl,

Thanks for your response.

CH was sitting at 290 the last time I checked and that was about a month ago. My CYA has been around 60 but at one point I did accidently put too much in and it got up to 90. I did some draining and now it's sitting at 60. Would those factors make a difference?

I'm not sure what SWCG is but I do know that we have chlorine tab reserve that we put 3 inch chlorine tabs in and then use the dial to control how much we want to enter the pool (1-4 dial).

So are you saying to add the 74 ounces of muriatic acid and not do anything with the Alkalinty and just see what happens?

Your CH is fine at 290.
CYA at 60 means you shouldn't use Tri-Chlor tablets or Di-chlor powder: your stabilizer is fairly high and you need to maintain your free chlorine (FC) between 5 and 10, and if you need to shock, raise FC to 20.
SWCG=Salt Water Chlorine Generator. If you don't have one, you don't need one (they are convenient but expensive).

Total Alkalinity (TA) is connected to pH. I won't explain how (not sure I can) but they are. Most ways that you raise or lower pH raises and lowers TA as well.
So when you add the Muriatic Acid to lower pH, it draws down the TA as well. When you add baking soda (that's all Total Alkalinity Raiser is) it pushes TA back up.
Therefore if, when you lower your pH and you see your TA go down as well, if you do NOT add the baking soda, TA won't rise, at least not as much.

TA is generally a pH buffer to help keep it from dropping too much, or rising too much and you push your TA the opposite direction of you pH trend. So if pH were to keep falling, we'd suggest raising TA.
Since yours is rising, consider lowering TA and see if that helps.