How low can TA be

[cschnurr]

I have an SWG for the past two years and have always had to add quite a bit of acid to maintain pH. I've seen in several posts that lowering TA and adding borates can help this problem.

During my first year as poolowner, I had TA of over 200 and I was adding a acid weekly. Last year, my 2nd year, I reduced TA down to 120 using the method described on this site, and my acid consumption decreased to a reasonable level of every 2-3 weeks.

I'm just opening my pool and have a low pH, so now would be a great time to lower TA. Will lowering TA some more reduce my acid usage. I couldn't find a recommendation as to how low TA can go and what is the risk. I do remember someone suggesting to another member that they might want to raise TA in order to keep the sparkling water look.

My measurements at opening were
Cl-0
pH-7.2
CH-250
TA-100
CYA 40

Since these measurements I've started shocking the pool and will add some CYA to get it up to around 60 for the SWG.

As much as I trust your expertise, I'm going to pass on adding borates for the very reason I came to this site... I just don't feel comfortable putting anything into my water I don't understand. I'm just too new at this to get my head around that borate thread. Maybe next year.

[dawndenise]

Currently, I'm struggling to maintain a TA reading of 80. My pool is almost a year old, but the SWCG came online about 2 months after the pool was built.

My scenario goes like this...pH 7.5, TA 60. Add baking soda to raise TA. Then pH goes to not-quite 7.8, TA 70. Add more baking soda to get TA to 80 but now pH is a solid 7.8 or 7.8-plus. Add muriatic acid to reduce pH to 7.5 and then TA falls to 60 again. This cycle happens once or twice a week, so I'd be very happy to have your schedule of adding acid every 2-3 weeks. I do have a waterfall which "helps" to lower my TA on a regular basis.

I'm not a candidate for borates due to having a dog drinking a fair amount of pool water.

Whether at 60 or 80, my pool still looks nice and clear. But, like you, I wonder how low my TA could go and still be OK.

[chem geek]

So long as you don't use acidic sources of chlorine, like Trichlor (or even Dichlor) and you don't use a regular non-chlorine shock (monopersulfate) which is also acidic, then a very low TA is no problem. You could even go as low as 50 ppm. You just have to compensate (in a plaster/gunite pool or a pool with a tile line with grout) by maintaining a higher CH, pH or combination of the two.

When your pH is 7.5 and your TA is 60, do not add baking soda. Leave the TA alone where it is. With a CYA of 30 ppm (that I'm guessing you have), then you can just have your target pH be at 7.7 and you will be in perfect water balance, though having it at 7.5 is just fine as well (at 7.7, there will be even LESS of a tendency of it to rise further and you'll need less acid to keep it there).

The bottom line is that a TA of 60 is perfectly fine for your pool.

Richard

[dawndenise]

Thanks for the info. Good to know that 50-60 is not too low. I'd like to post a full set of numbers and get your feedback but I don't want to hijack Carl's thread so will post a new thread.