Variance in TA reading

[saraiks]

I tested my TA with the TF test kit and it read 70.
I retested with my old Leslies kit and it reads 100.

Is the TF test kit test reading accounting for the CYA(60) ? or is someting else whacked..

 

[rimshaker]

Key word being "old."

How long have you had the Leslies kit? The reagents may have aged.

 

[saraiks]

The Leslies kit is old but the reagents in it are fairly new...

 

[duraleigh]

Saraiks,

Assuming the tests use the same chemistry (do they?), you could stretch a little and say those results are within limits (almost).

If TF was off by one drop (low) and Leslie's was off by one drop (high) they'd be within 10 of each other.

Again, I think that's a bit of a stretch but not unreasonable.

My experience with the Alk test has been it's pretty accurate and repeatable. It would be interesting if you got the same test discrepancy twice.

 

[saraiks]

I trust what the TF test kit is telling me but wanted to know what the other kit was reading.

The test procedure for the other test kit is fairly similar.

Fill up Water to a certain mark on the measuring cylinder.
Add a drop of Chlorine neutralizer.
Add 2 drops of the #4 reagent.
Add #2 reagent and count drops. TA is 10X no of drops.


I have tried it at least three times with the same results each time. TF kit reads 70 and the Leslie's reads 100.

 

[duraleigh]

It sounds like the Leslie's test uses less (volume) reagent and perhaps less pool water. I wonder if you doubled the "recipe" in the leslie's test if the results wouldn't be closer. That's just a guess but may have some merit.

I have never compared the Alk test results of the TF-100 with other tests....might be interesting to do.

If a pool store is close by, and they don't use strips, you might get a third opinion although I would trust your own results over most pool store testing.