TA before and after borates

[camueller]

Hi all, I'm trying to make sure my pool is stable pH wise before adding borates. I've determined that my pool is nice and stable at 7.5pH and 60ppm TA. Problem is, my fill water is high in TA, and through adding replacement water over the last 2 weeks I've increased my TA to 80ppm. My pH is still 7.5, but I want to get my TA back down to 60ppm so I can add borax.

So, I'm wondering, can I just add acid to knock my pH down to 7.2 or maybe 7, and use borax to raise my pH back up to 7.5, repeating if necessary?

Using pool math tells me it won't take too much borax to get my pH back where I need it, and it'll add like 1.5ppm TA. That got me thinking, when I add enough borax to get me to 50ppm, I'll be adding enough borax that it'll add nearly 100ppm TA. So if I start adding borax around 60 ppm, what am I going to end up with? Will some of the acid I also add in with the borax eat up some of the other TA, balancing things out in the end?

 

[pooldv]

That is some interesting thinking. I don't know. I'm going to get some help on this so we can both learn something maybe.

I have the same issue with high TA fill water raising my TA.

 

[duraleigh]

Well, it sounds like you want to use the procedure to lower TA found in Pool School. Won't that work?

 

[camueller]

I used the lowering TA method for a week to get myself down from 200ppm to 60 ran at that for nearly 2 weeks stable until I had to add more water, and then my TA went up again. At this point, I'm not trying to lower TA to learn where I want to be, I'm just trying to get there so that I can add borax. And my thought is if I'm going to be adding it anyway, why not take advantage of it's ability to raise my pH rather than run my home made fountain for 36 hours to get me back up (maybe). It takes a lot longer to move my pH with aeration now that my TA is lower.

This morning my pH is 7.2 after adding some MA last night to eat up TA. My TA is still at around 70 though. I'll use today to decide what I'm going to do, then go for it tonight. But I'm leaning towards using the borax and not waiting on the aeration.

 

[pooldv]

Using the Effects of Adding Chems toward the bottom of Poolmath it says 1lb of borax in 20k gal will raise PH 0.38 and TA 6.8. So, that isn't going to be all that helpful.

 

[JoyfulNoise]

Borates act as an additional buffer and they have their greatest buffering strength as the pH increases. So if you lower you pH with acid to reduce TA and then add borax to raise the pH, it will get progressively harder each time to lower the pH (takes more acid) because you will be working against both carbonate alkalinity and borate alkalinity. My suggestion would be to lower your TA again but use boric acid instead of borax. It dissolves much faster, lowers your pH only a small amount and can be added all at once.


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[camueller]

If my TA is 60 now (I'm not sure it is, but let's just say it is) and my pH is 7.2, then to me adding 1lb of borax to get my pH up by .38 sounds perfect. That would put my pH at 7.58, increase my TA by 6.8, and seemingly put me in a good spot to start adding my borax and MA. From what I've read, adding it all to my pool will cause a "very slight" increase in TA overall, but I'm curious how slight that'll be. I guess I'll take notes and see.

I already have 15 boxes of Borax on hand plus 5 gallons of MA, so I don't want to reverse course and do the boric acid instead. I found it all cheap enough that price came out the same if not cheaper than ordering from Duda Diesel, and though I know it'll be harder this way, it doesn't sound that complicated.

I've got my home made fountain running while at work. I'll see what the pH and TA are when I get home and decide what to do from there. With my high TA fill water, I'm worried that adding borates may cause a struggle with maintaining my TA where I want it. But then again, where I want my TA is somewhere that the pH isn't rising on me too fast, and maybe that number is higher with the borates in the water. I guess once I've got this stuff added, I don't really need to worry about my TA again until I notice pH problems.

 

[JoyfulNoise]

Overall your TA will rise about 10ppm or so. You may not even be able to see it on the test.


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[camueller]

Fair enough.

In my mind, if I'm ready to borate, but I want my TA to be a little lower before starting, as long as I keep the pH above 7 I can take advantage of all the MA and Borax that I'm about to dump in there by staggering my start of chemical addition to let the MA get to work before the borax does. That may not even matter, but if it makes me feel better, then what the heck.

Thanks all! I'll post back the results and my numbers before and after, in case anyone else finds this thread in search of the same answer some day.