True Total Alkalinity Reading?

[isabelo]

Having read about this "True Total Alkalinity Reading" value and it's formula -> TA - (CYA/3), should I consider it with my water tests?

In the Pool School Recommended levels for Plaster (with Bleach), TA should be 70-90+ ppm. But if I pay attention to this "True Total Alkalinity" formula, and if my CYA is about 30 ppm I end with some value that is almost always less from just reading the TA results from the TF-100 test kit.


For example:

From TF-100 test kit reading: TA = 100 ppm

From "True Total Alkalinity" formula -> TA - (CYA/3):

> = 100 - (30/3)
> = 90 ppm

So, is my TF-100 test kit's TA reading of 100 ppm good enough because if plug it into "True Total Alkalinity" formula it equals to 90 ppm? Or should I discard this "True Total Alkalinity" formula and only pay attention to my TF-100 test kits, TA reading alone thus my TA still needs to be dropped by 10 ppm?

 

[Richard320]

Who says your alkalinity needs to be reduced by 10?

If you go to poolmath and go to the last row where it says Suggested Goal Levels and you choose trichlor as your chlorine source (you DO list a Rainbow 320 Chlorinator, after all) recommended TA is 100-120+

If you're using bleach, then TA suggestion is 70-90+ . You're at 90+ already. You're fine.

Poolmath takes various forms of alkalinity into account in its calculations. See True Alkalinity Readings or try the search box for more.

 

[cowboycasey]

I think you are getting in the weeds unless you really want that kind of info..

It only matters to drop your TA when your PH is rising fast.. you are trying to stabilize your PH as much as possible to keep around 7.6... so if your pH is doing good then TA of 100 is fine

 

[isabelo]

Who says your alkalinity needs to be reduced by 10?

If you go to poolmath and go to the last row where it says Suggested Goal Levels and you choose trichlor as your chlorine source (you DO list a Rainbow 320 Chlorinator, after all) recommended TA is 100-120+

If you're using bleach, then TA suggestion is 70-90+ . You're at 90+ already. You're fine.

Poolmath takes various forms of alkalinity into account in its calculations. See True Alkalinity Readings or try the search box for more.

I do list a Rainbow 320 Chlorinator, but stopped using that when it caused problems with my check valves and gas water heater (see - Badly mangled Pentair check valve flapper) about a year and a half ago. So I have been using Liquid Chlorine ever since then. Therefore, the suggested goal TA level stays the same at 70 to 90+ ppm consistent with Pool School. So, the same question I raised above - 'Should I even bother taking the "True Total Alkalinity" formula into account'?

 

[isabelo]

I think you are getting in the weeds unless you really want that kind of info..

It only matters to drop your TA when your PH is rising fast.. you are trying to stabilize your PH as much as possible to keep around 7.6... so if your pH is doing good then TA of 100 is fine

Yes, my TA was about 120+ ppm about three weeks ago and pH have been inching in the upper bracket faster than I would like. So I have been lowing the TA to get to about 90 ppm (from Pool School Recommended Levels). My thought is to get TA to at most 90 ppm since my City Water source is high on pH to start with.