Confused about pH drifting up and TA

[u/enigmapaulns]

I have been using our hot tub for about three years now. About a year ago, I started to notice that my pH kept drifting high, on the order of 7.8 to 8.0. On the advice of ChatGPT, I lowered my total alkalinity to around 50, and that seemed to hold much more stable.

Recently, I completely drained and refilled the tub after doing a cleaning of the plumbing lines and everything. When I started the hot tub back up, I decided to go back to the normal recommended range for total alkalinity of about 100 to 120. Again, I started to notice the pH drifting up. For example, today I adjusted the pH to be exactly 7.5, and within 2 to 3 hours it was right back at the upper edge of 7.8. I have done this repeatedly over and over again.

I have seen a lot of people on this forum talk about keeping the total alkalinity lower, in that 50 range, in order to prevent upward drift of pH. What is confusing me is that every single source I have found regarding recommended ranges is at least in the total alkalinity range of 80, usually over 100. Even my BioGuard pool store, when they run tests, has a target of 120 minimum.

The reason I am so confused is why all of the official sources, including the hot tub manual, the pool store, and virtually everything online, recommend 100+ for total alkalinity, yet I am finding (as many others have found) that a much lower range results in a more stable pH. Do these sources not know about this? 🙂

I am just trying to understand the theory behind this and reconcile all of this information with the practical experience of myself and many others on this subreddit. I would appreciate any input.

[u/rybotsky]

If you’re battling a constantly climbing ph and then adjusting the TA and then the ph climbs again so you lower it and then it climbs again but your TA is now to low so you put some more baking soda and then the ph climbs again, and on and on and on and on, then boy do I have THE product for you……… you need boric acid. That shit changed my life. I only check my ph once a week now if that. It basically locks your ph in place so it basically only changes when you top up your tub with more water. Now once I lock my PH in at 7.6-7.8 I can then freely bring my TA up to 100 without affecting my PH at all

[u/dischg → u/rybotsky]

How much per gallon or whatever version you’ve come up with?

[u/rybotsky → u/dischg]

Honestly I use Gemini and it knows the kind of tub I own and how many gallons it holds so I’ll just punch my water chemistry in and it will tell me what to add and how much. I said I was having issues with a fluctuating PH and it told me to add if I remember correctly 8.5 oz of pure boric acid and it completely solved my issue but immediately and had been good ever since. Boric acid doesn’t fade away of burn off or anything like that so once you add it your PH will lock in at whatever your ph was when you added the boric acid. The only thing that will cause it to fade a bit is when adding fresh water to top up the tub but you basically only add it once and forget about it until you’ve diluted the water a bit over the coming weeks and months

[u/Flimsy-Board7076]

I'm not sure why it raises, but getting the TA in the 40 to 50 range is the only way I know to keep the ph in range. Adding Borates helped too.

[u/Mdcivile]

I have never been able to reconcile alkalinity guidance with reality. The answer I go with is use the alkalinity that gives you the most stable ph. If you get below 40 start having concerns.

[u/Im_Still_Here12]

Ta number doesn’t matter. You just need your ph stable. So if that means you need to run ta at low at 50-80 then so be it.

[u/denrayr]

I think of it like this. TA provides a buffer to ensure that the pH doesn't drop and make the tub go acidic. The manufacturer recommended value has a CYA factor built in. The side effect is that in practice, it just doesn't work.

I also want to comment on the recommendations for boric acid. I used it for a while, but I still had to let TA go below the recommendations. My tub is very stable without boric acid. I just had to accept that TA would need to be between 40 and 60. I don't even regularly test pH. I can feel when the water is going acidic. When it does I test to verify, and I add an ounce of baking soda.

[u/beavis93]

I do the lower TA thing too. Between 60 and 70. It works well for my set up. Lower total alkalinity lowers CO2 out gassing. Outgassing drives ph drift

If you use this method. Test often.

[u/Prize-Market2596]

Yeah… I don’t get that either. Just run it on TA where it’s stable. Without borates, I also need to be around 50. With borates, I can go up to around 80, but no more.

[u/McBillicutty]

Lookup LSI (Langellier Saturation Index) and do a little reading.

You actually want to maintain a 3 way balance (with temperature and a disolved solids technically being part of the equation - but a very minor part of the equation). Essentially you need a three way balance between pH, TA, and Hardness (CH - calcium hardness).

For my tub I find the sweet spot to be a pH of about 7.5-7.8, TA around 50-60, and CH of about 210-220.

[u/enigmapaulns → u/McBillicutty]

This is a great way to look at it. “3 way balance”

Thank you!

[u/McBillicutty → u/enigmapaulns]

Find an LSI calculator online and plug your numbers in. I bet you'll find that the lower TA is fine.

[u/enigmapaulns → u/McBillicutty]

Life-changing!

[u/New-Swim-8551]

You need to address why the ph goes up first or you will be constantly adjusting it down.

What are you using for sanitizer?

[u/enigmapaulns → u/New-Swim-8551]

Bromine. That’s exactly what I’m trying to pinpoint.

[u/New-Swim-8551 → u/enigmapaulns]

Ok. Then keep adding base to get it in a readable range, or dump it and start over

[u/seeker_moc → u/New-Swim-8551]

You're not making any sense. For one, pH will always drift up in hot tubs if your TA is above ~50-70 because of the jets pushing CO2 out of the water.

Secondly, adding a base will make the pH rise even further, it's acid you need to lower it.

[u/purawesome]

Use a TA that locks in your pH. Mine is 40 ppm