Hi, new to the forum.

Anyway, I have a Caldera Tahitian tub. It has a CD ozonator. I use a 2006 for testing.
Here are the numbers:
CH 110
TA 110
CYA 35
CC usually 0.0 to 0.5
FC 0.5 to 5

And right now the pH is 8.0, I bring it down to 7.5 every 24-48 hours and it just goes back up.
I tried 80 TA and that didn't help. Also I am getting a decent amount of scaling but I assume that's from the high pH.

I sanitize with dichlor or bleach. What is going on here? Any help will be appreciated.

Welcome to TFP!

You need to go far lower than 80 ppm with the TA, as low as 50 ppm if necessary. The ozonator doesn't help the pH situation because it aerates the water more. Even though a very low TA may help, it also reduces overall pH buffering so using 50 ppm Borates (from Boric Acid such as in Proteam Gentle Spa) can help with that to give you pH buffering that doesn't outgas carbon dioxide and cause the pH to rise.

You should try to keep your minimum FC level (except, perhaps, during the soak itself) at 1-2 ppm and not let it get below 1. You can then add more chlorine right after your soak such that you still measure a residual before the next soak. 0.5 is close to zero and if for some reason your bather load is higher and you get to zero for too long, then biofilms can form and be much harder to get rid of than planktonic (free-floating) bacteria.

I used to have the same issue in my hot tub. I used to think that having the TA around 100 - 120 was the proper way to go. Now I use borates at 50 ppm and keep the TA around 60 and my pH is pretty stable. Another thing to be carful of is to ensure you turn off the air injection when you are not in the hot tub. Injecting air into the tub will aerate the water further increasing the pH. If you don't turn it off every time the hot tub does a maintenance cycle for heat or filtration you are going to be aerating the water increasing your pH.

Thanks for the responses. I will bring the TA down a bit and see if that does it.

PH climbing from 7.5 to 7.8-8.0 each week normal?
I keep the TA at 60 now.

If your pH is constantly increasing, then your TA is too high. If your pH is constantly falling, then your TA is too low. When your pH remains stable, then your TA is just right. You can take the TA down to 40 if you need to.

I recommend a pH of 7.7 to 7.9, which won't cause scale as long as your CSI is kept slightly negative. Use the pool calculator to calculate your CSI.

Adding borates from boric acid will also help. 3.82 ounces of boric acid per 100 gallons of spa water will add 50 ppm borates.

If you are using aeration jets in the spa, then the pH will tend to rise more. Using the borates (boric acid) will slow down the rate of rise, but not the amount of acid you need to add. Lowering the TA some more might help a bit. Dichlor is net acidic so shouldn't be rising in pH so much, but the bleach that you are using might have a lot of excess lye in it. Clorox Regular unscented 6% bleach that has "5.7% Available Chlorine" on the label has the least amount of excess lye so will have less of a pH rise in a heavily used spa.

When you are not using the spa make sure the air is turned off on all the jets. If you leave the air turned on it will mix with the water and cause the pH to rise faster even when you are not using the spa.

Yup, air is always off when not using it.
I think I got it to stabilize now.
Thanks.