Low Alkalinity

sammm

LifeTime Supporter
May 10, 2007
257
North Richland Hills, TX
#1
I just tested my water. Everything is 'normal', except my alkalinity seems low (60). PH is ~7.4. I only use bleach and have to add acid occasionally to bring the PH down (normal, right?).

Is an alk of 60 too low? I've added baking soda in the past and got it up around 80 or 90, but it slid back down. Should I care? TIA!

PS
Water looks great and is crystal clear.
 

chem geek

TFP Expert
LifeTime Supporter
Mar 28, 2007
12,082
San Rafael, CA USA
#2
A low TA is actually not a problem and will help reduce the amount of acid you need to add to keep the pH where you want it. The only issue is that it reduces the saturation of calcium carbonate in the pool, but that only matters if you have a plaster/gunite or similarly surfaced pool (or any exposed grout with tile). For a vinyl pool, for example, it doesn't matter. For fiberglass, you should have some Calcium Hardness (CH), but don't need to be at full saturation (we think). If you have a plaster pool, then it's easy to compensate for the saturation through a slightly higher pH target and/or a higher CH level.

If your CYA level is low (say, around 30 ppm), then I wouldn't worry about the TA until it gets to 50 ppm. I would still keep it above that, but you should find that it drops rather slowly over time. And just be careful about adding any acid to the pool -- it will take less to move the pH due to the lower TA (and that includes acidic sources of chlorine such as Trichlor and Dichlor as well as non-chlorine shock).

By the way, do you have water aeration features such as a waterfall, spillover, fountain, air jets, etc.? Or do you get a lot of summer rains (raindrops splashing cause aeration)? Pools are intentionally over-carbonated, just like a carbonated beverage (though obviously not THAT carbonated!) so outgas carbon dioxide to the air and that process causes the pH to rise (with no change in TA). Then, adding acid to lower pH also lowers the TA. You may also find that having a pH target of between 7.5 and 7.7 will help compared to trying to maintain 7.4.

Richard
 

sammm

LifeTime Supporter
May 10, 2007
257
North Richland Hills, TX
#3
Thanks as always Richard for a great explanation! 8)

We do have a water fall, but I usually have it off. I have it turned off most of the time because my system only has 1 pump and it 'takes away' from my Polaris. We did have an extra wet summer this year in the DFW area as well. My CYA was ~40 last time I checked it, so that makes sense too. I'll just go with a slightly higher PH and move on. Thanks again!
 

matj6876

LifeTime Supporter
Jul 28, 2007
105
DFW, TX
#4
Sammm - just for peace of mind. I'm in the DFW area too, have similar numbers and a low TA.
It don't help you much but at least you know you're not alone! :-D