What should my TA be at? Conflicting info in threads and chart

[Skenn81]

Specs in signature. K-2006 test kit.

I have always gone off the chart here: Pool School - Recommended Levels

It says for a plaster pool TA should be 70-90+, so I went with the "+" and have always kept it around 100. Not sure why but I must have read it someplace when I started on the TFP methods and have just always left it there. On some threads that were surfacing about rising pH levels, which is the thing I keep noticing in my pool, folks say keep it down at the 50 or 60 level.

So where should it actually be? Is the "+" in the chart mean I can keep it high or should I drastically drop the pH for a while to get that down?

Others..
CL kept around 7
CYA currently about 40
Calcium Hardness 320 last check a couple of weeks ago.
pH I try to get down to 7.6 but always wanders back up to 8.

 

[ajw22]

There is no one right number for TA. TA as a stand-alone number doesn’t matter. TA matters in the relationship to your PH rise. The higher the TA, the more rapid the PH rises over time. If you want to reduce how rapidly your PH rises then let your TA naturally decrease as you lower PH. If you are fine with your PH management then you can leave your TA alone.

 

[JoyfulNoise]

The way I look at TA, pH and CH is to manage them according to my CSI (saturation index). TA and pH are easily changed, CH takes a bit more work. But in the end, for a plaster pool, managing saturation is key to not getting calcium scale or plaster damage. I always aim to keep my CSI slightly negative (-0.2 to 0) and so there are lots of combinations of pH, TA and CH that will do that. My other goal is to keep my pH rise to a minimum so I’m not constantly having to add acid to the pool. So, with those two goals in mind, keeping, my TA lower (around 60ppm) allows me to achieve a low pH rise as well as keep my CSI in a slightly negative range. So, when my pH swings from 7.5 to 7.8, that’s totally ok as my CSI remains where I want it to be and my acid additions are limited to every 10-14 days.

What this all comes down to is this - pool water parameters (pH, TA, CH, etc, etc) are inter-related on different levels and so you can’t think of them as totally independent quantities, ie, there is no one “correct” number. Ranges of values are absolutely necessary to keep a pool simple and easy to maintain.

 

[Skenn81]

With the ranges on the levels page over at Pool School - Recommended Levels should I just try to stay in the middle of the range? The TA is the one with the + on it so I thought it meant go higher but the results I now find are rising pH levels. In the mean time I am bringing the pH down to 7.4 for a while, below my usual 7.6 to try to bring it down.

 

[Texas Splash]

The TA is the one with the + on it so I thought it meant go higher

The + symbol simply means the TA "can" be higher if needed. As Matt noted, depending on the pool's CSI (water is corrosive or potential to scale) and/or the rate of pH increase throughout the week, we adjust the TA as best suited for our pool. Of course the PoolMath helps. In general, as long as you keep all of your parameters within the TFP Recommended Levels ranges, you should be fine. So to answer your last question - your last TA was about 100 correct? That's fine as long as the pH doesn't rise too fast and/or your CH isn't too high which (together) all can increase the potential to scale. Not sure if you get the large amount of water exchange in central FL like some others which can change those levels, so simply monitor and adjust as necessary. Some of the "other threads" you mentioned where folks keep their TA low was probably because they are in a location with very hard water and/or their pH simply rises too fast. As such, the lower TA helps - for them. Each pool is different.