Alkalinity, pH relationship

[Racoon293]

Hello All,
New hot tub owner and first post.
I’m struggling with high pH in my hot tub.
TA- 110ppm
PH- off the scale high
Total Bromine 5ppm

Adding small amounts of pH down at a time tends to lower the Alkalinity but not the PH.
Should I just keep going until I get my pH where I want it and worry less about the alkalinity?

 

[Texas Splash]

Welcome to TFP! Well, you certainly do have much more room for the TA to fall. You could probably go down as far as 50 if you really needed to. But for now, I"m assuming the "pH Down" product you are mentioning is a pool store product? If so, I would recommend switching to muriatic acid (MA). Cheaper and may have less byproducts in it. It won't take much in a 400 gal tub, so make sure to use the PoolMath tool (or APP) for dosage amounts. If you're concerned about the strength of 31.5% MA for such a small tub, there is a 15% strength that is available.

The rate of increase for your pH depends on several factors, most notably if the TA is elevated and amount of tub use (aeration). I would also recommend adding to your signature which test kit you are using for those numbers and that will drive the replies you receive as well. Enjoy the weekend!
ABCs of Pool Water Chemistry

Hot Tub Basics - Further Reading

www.troublefreepool.com

 

[jseyfert3]

You will need to drop your TA to keep the pH rise manageable. Most people tend to need to drop it to 50-60 for best stability. In my own experience at a TA of 100+, if I add enough acid to drop the pH to say, 7.2, it will be above 8 again with just 30 minutes of running the jets with air turned on.

To lower TA use Pool Math (phone app or desktop version) to figure out how much acid to add. Use a pH of 8 with a target of 7.2. Add acid, run all jets with all air valves open. Run till the pH is back to 8 (30-45 minutes). Check TA, repeat process until TA is roughly 70.

At this point the pH rise should be manageable. Add acid as needed to lower pH, but now only target a pH of 7.6. Let the pH hang out between approximately 7.6 and 7.8. Trying to maintain less than 7.6 can be difficult.

Hope this helps. Let me know if you have any questions, I've done this a few times.

 

[Racoon293]

Thanks for the advice.
I use a combination of 7 way pool store brand test strips and and a Pool Master 5 way liquid test kit for water testing.
Is Muriatic safe for an acrylic shell tub assuming directions and procedures are followed?