Different Total Alkalinity tests

[pandan74]

I have question about TA results. I finally got my TF-100 and that test shows TA 120, I also have BioGuard test (previous owners left that test behind) which gives TA 70, I have also results from 3 different pool stores (I know what do you think about their tests) but their results (from all 3: Leslie's , and 2 local stores) were TA = 30. People form the local stores suggested to increase TA by adding backing soda (from Costco) only Lesli'e suggested their product. The difference 30-120 is significant. The pH goes up from ~7.2 to ~7.6 and it needs to be adjusted usually twice a week by adding 1.5-2 cups of MA (9,000 gallons). My question is why the TA results are so different and which one I should trust.

I just tested water (TF-100):
pH 7.2
TA 120
FC 9.5
CC 0.5
CH 625 (I hav been using Cal-hypo but just switched to bleach - no more Ca2+ added.
CYA 70-80

 

[mknauss]

Did you follow "Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by wipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop."

 

[mknauss]

Also, the pool store tests are 'adjusted' alkalinity. TFP does not use that. Poolmath manages that for us.

The other test kit you have may be pretty close. Redo the TA test as described above. After you do the test a couple times, the static issue disappears.

 

[pandan74]

Did you follow "Sometimes a static electric charge can build up on the R-0009 dropper bottle tip, causing the drops to be smaller than usual and making the test read higher than actual. You can prevent this by wipping the tip of the dropper bottle with a damp cloth or tissue before you start and after each drop."

Yes, I do use a damp paper towel and wipe the tip of the bottle after each drop.

 

[pandan74]

Also, the pool store tests are 'adjusted' alkalinity. TFP does not use that. Poolmath manages that for us.

The other test kit you have may be pretty close. Redo the TA test as described above. After you do the test a couple times, the static issue disappears.

Other numbers are quite close, TA is the only "problematic" one.