Low Alkalinity ?

[gyoungers]

Earlier in the summer my TA was running around 80-100ppm and I needed to add about 2 cups of acid every 2-3 days to keep the pH within range (7.5-7.6 as a target).

I've only had to add acid on a regular basis the entire season, everything else was in line and really left alone.

Now as fall as arrived, my TA is at around 40-50ppm and I've noticed a drop in frequency of acid additions (expected).

The last full set of test results I performed:
=====================================
pH = 7.5
TA = 40
CH = 400
CYA = 50
TC = 3
CC = 0


Are the additions of acid slowing dropping the TA over time?
I know it may not be great to have the TA that low, but what are the dangers in having it at this level?


Thanks.

 

[investindy]

Yes, please see the pool calculator at the bottom, Effects of adding chemicals......Select MA and you will see the impact of TA. Its an awesome tool. I learned the hardway about CYA additions due to my shocking products and the calc proved it.

http://www.poolcalculator.com/

 

[meatloaf]

If I understand the above posts correctly, a lower alkalinity will in turn reduce the need to add acid to lower PH levels? :?:

 

[JasonLion]

Adding acid does indeed lower the TA. Each acid addition usually only lowers the TA a little, but over the course of a season it can add up.

Lower TA levels reduces the rate of PH increases from CO2 outgassing, and lower TA also means that it takes less acid to change the PH by a fixed amount, both of which are why you aren't using as much acid as you were earlier in the season.

As your TA level goes down, the PH will change more rapidly in response to chemical additions/debris/swimmers. If the TA level gets too low it becomes difficult to maintain a consistent PH, as practically anything added to the pool, say some blown in leaves, becomes enough to shift the PH noticeably. Lower TA levels also lower your calcium saturation, which can cause damage in plaster/pebble pools if your PH gets too low (a bit below 7.4 with your current numbers).

For these reasons, it is normally best to keep TA at 60 or above. Several people have experimented with TA around 50 without any significant problems. Having TA lower than 50 raises the risk of something going wrong significantly.

 

[meatloaf]

My TA is @ 110 currently (pool temp 70*) and I usually add 5-6 oz of MA daily to maintain a PH of 7.6. If I lower TA to 70-80, will that help to reduce the amount of MA I have to add daily?
Is there a happy medium somewhere?
Thanks

 

[JasonLion]

Yes, lowering TA from 110 to around 70-80 will reduce the amount of acid you need to use. Constantly rising PH can come from various sources. High TA is the most common, but some acid demand may remain depending on other factors. TA around 70-80 is a good TA level for most pools (unless you are using trichlor pucks, which requires higher TA levels). Pools with extreme amounts of aeration, for example a negative edge, may want to lower TA a little further.

Keep in mind that plaster that is less than one year old will require regular acid additions while the plaster cures, regardless of your TA level. Plaster pools that are more than one year old, and pools with other surfaces, can usually have their levels adjusted to greatly reduce or even eliminate the need for regular acid additions.

 

[meatloaf]

Thanks, so if I understand this correctly, I should lower my TA. Is this a good time to do it even thought the pool temp will be dropping for the winter? :?
Also my CSI has been holding around -.01 to .03.

 

[meatloaf]

Started do drop my TA. Current reading is TA 90 (from 110 yesterday) PH is 7.0 and my areators are on. Hopefully this will lower my doseage of MA per day. Do you think I will have to go lower than 90?

 

[Guest]

If you are using primarily a stabilized form of chlorine (trichlor or dichlor) then adjusting the TA to around 100-120 ppm helps counteract the pH drop caused by these products. When using an unstabilized chlorine (sodium hypochlorite or bleach, cal hypo, or lithium hypochlorite then adjust the TA to between 70-90 ppm. Perhaps this would be a good time to review the information in Pool School since it's all right there!
category/pool-school/recommended_levels
Rereading it now might answer more of your questions and you will probably have a better understanding of the material!

 

[meatloaf]

Thanks, I'll reread it again. Hopefully I'll understand it better this time.
EDIT: Now I understand. I forgot that I have recently changed from Tri-Chlor to the BBB method.