pH or TA but can't have both

[Zeeohsix]

Hello all,

I'm having a Dickens of a time trying to get my hot tub's water balanced and was hoping for some insight.

I have an Artesian 500 gallon 62 jet tub and am using the Bromine 3 step system as a sanitizer. Unfortunately for some reason I can't get the pH and TA to play nice together. After my recent drain/fill and before adding anything my readings were :

CH. 50
pH. 7.4
TA. 40

Everything I've read says the TA is on the low side so I added Alkalinity booster to bring it up to 80 but my pH then jumped above 8.2. So, I added enough pH decreaser to bring it back down to the low end figuring I should be able to adjust the TA from there. After I got the pH back down to 7.2 my TA was 30 so added just enough Alkalinity increaser to bring it 60. Unfortunately my pH is back up to 8.2. It seems as though I only have one choice, either a good level for the pH with a TA below 40 or a decent level for the TA - starting around 60 but with a pH above 8.0.

In the past I've also tried starting off with the levels right out of my hose, pH of 7.4 and TA of 40 but after a week or so the pH started to rise so I assumed the Alkalinity level was too low to stabilize things.

I'm using a Taylor test kit so readings are very accurate.

The spa is only used occasionally 3-4 nights a week for approx 20 minutes each time with at most 2 people in it.

Hoping someone here could offer suggestions or tell me what I'm doing wrong.

Thanks in advance

Ray

 

[triptyx]

In a hot tub, the pH will always rise as you use it - the bubbles aerate the water and raise pH. As you add acid to lower the pH, you're also lowering the TA. You will not be able to "stabilize" pH to where it never rises if you're using the hot tub (and not introducing acid through some other means such as solid chlorine products).

My suggestion is to bump TA to 60, then adjust pH to 7.8. pH is logarithmic, so by trying to force it down to 7.2, you're having an adverse effect on your TA. Keep pH at 7.8, when it gets to 8.0, lower it to 7.8 again. You could also consider maintaining it at 7.6, but definitely do not keep trying to send it to 7.2 and attempt to keep it there.

 

[ant 83]

Here is what I do.

I test PH before adding chlorine.
If PH is higher than I like it, I add a small amount of acid.
I then wait until the next day to test PH again.
Repeat.

Some bromine tabs are acidic though I thought. In that case, I'd do the same thing, but add buffer if the PH was lower than I'd like.

The recommendations for testing TA, and the numbers given are aimed at people useing dichlor I think. Dichlor works as an acid, and the spa people are worried about falling PH corroding heaters, that they then have to replace under warranty. They advise a TA that is too high for a margin of error. This is necessary with people measuring PH with the inaccurate dips strips they like to sell.

Just focus on PH, and add what you need to to keep it where you want. Test frequently.

 

[Zeeohsix]

Thanks for the info guys, very informative. I guess I'll concentrate on my pH levels. My concern was that everything over been reading has said the TA should be between 80-120 in order for it to act as a buffer for fluctuating pH levels. It's just that anything over 40 and my pH would rise above 8.0. So for now I'll get the pH to 7.8 and see what this does to the Alkalinity.

 

[calisoldier]

Here is what I do.

I test PH before adding chlorine.
If PH is higher than I like it, I add a small amount of acid.
I then wait until the next day to test PH again.
Repeat.

Some bromine tabs are acidic though I thought. In that case, I'd do the same thing, but add buffer if the PH was lower than I'd like.

The recommendations for testing TA, and the numbers given are aimed at people useing dichlor I think. Dichlor works as an acid, and the spa people are worried about falling PH corroding heaters, that they then have to replace under warranty. They advise a TA that is too high for a margin of error. This is necessary with people measuring PH with the inaccurate dips strips they like to sell.

Just focus on PH, and add what you need to to keep it where you want. Test frequently.

This. I always dial in my PH and use acid over the course of two days. Then once I'm at 7.6, I add borates to lock in everything. I also make sure to turn off my aeration until borates are added.