Taylors kit reads low TA

[gkarag]

I have a Taylors kit which is about 9 months old and lately the TS reading is consistent at 50ppm.
To increase TA I dropped Bicarb Soda and tested with sensafe meter which read about 80ppm but Taylors kit still stated 50ppm. Also had water tested at pool shop which cofirmed the sensafe measurement.
Is the Taylors chemicals gone off???

 

[Bama Rambler]

Which Taylor kit do you have?
Do you have a magnetic stirrer?
Are you dropping till the color stops changing?

 

[gkarag]

I have a Taylors FAS DPD test kit. I drop five drops of final solution and colour changes from green to red and stays like that.

 

[257WbyMag]

Here are some potentials that could be going on:

1. You have static built up on the dropper that is causing the drop size to vary. Wipe it with a moist cloth between drops to eliminate this problem.
2. Your sample size isn't consistent.
3. You are not adding drops until you have reached the true endpoint. It isn't over when you get red. It's over when you get red and adding more drops doesn't make it get any "redder".
4. You reagent is old or has been exposed to temperature extremes, therby rendering it ineffective.
5. Your Sensafe meter is wrong.
6. Both your Sensafe meter AND the pool store is wrong. I haven't found many pool stores that are right to begin with actually.

That about sums it up.

 

[duraleigh]

I would agree (almost) with 257's assessment and would arrange them by probability...

1. You are not adding drops until you have reached the true endpoint. It isn't over when you get red. It's over when you get red and adding more drops doesn't make it get any "redder".

2. Both your Sensafe meter AND the pool store is wrong. I haven't found many pool stores that are right to begin with actually.

3. Exposure to extreme moisture and sunlight condition could degrade the reagents but we have no other reports of that that I can remember.

3. It would not be from static buildup. static in the R-0009 is common when the chemistry is VERY fresh and results in smaller drops and would cause your Taylor test to read high.

 

[gkarag]

Thanks for info will investigate further.
I don't think sensafe meter is wrong because sensafe was 60ppm and Taylors was 50pppm.
I was a bit alarmed that TA was a bit low s I dumped about 2Kg(4.4 lb) and took another reading sometime later.
Sensafe was 80ppm and Taylors still 50ppm. My pool is about a year old and have been going through about 20kg(44lb) drum of acid every 2 months although this is starting to slow down. Intitially pool shop kept telling to push TA up to 100pm which after reading this site is excerbating the problem. So now I am aiming somewhere between 70 and 80ppm for TA. I am still experimenting but certainly I do not want to go below 60ppm for TA as I am concerned about the balance of the water. What I intend is to push PH up in winter to about 7.7 to 7.8 and drop to 7.4 to 7.5 in summer.

 

[chem geek]

I am still experimenting but certainly I do not want to go below 60ppm for TA as I am concerned about the balance of the water.

If your pH is more stable at a TA of 60 ppm then just leave it there. If you have a plaster pool, then you can always raise the saturation index by increasing your Calcium Hardness (CH) as well as your target pH. Note that if the plaster is new, then plaster curing will raise the pH and even a lower TA won't help with that. A lower TA only helps reduce the rise in pH that comes from the outgassing of carbon dioxide. If you have water aeration features that you can turn off, then that can help reduce the rate of pH rise as well.