TA differences

[hooeld]

I test my TA with a Taylor 2006 kit, and it was 160 on Apr 22nd, so I lowered my PH, and run the pume with the nozzles as far up as possible. It is not doing as much airation as I would like, but I thought it would over time, running the pume 24/7. Yesterday I tested with these results:
FC 9.5
CC 0
PH 7.2
TA 110
CA 260
CYA abt 25

I have been adding Triclor to keep FC at about 19, and boost the CYA just a bit to get to abt 30.

Pool is Plaster.

My question is this... My TA tests say 110. I took some water to a new Hardware store with a computerized testing setup, just to see how we compare. Their results are:

FC 9.6
TC 9.6
CC .0
PH 7.4
CA 160
Alk w/ stabilized correction: 0
CYA 25

Why do they show 0 fro Alk, and I show 110?? She run the test 2 times??

I also came home and run a alk test with a different test kit (bought at walmart last yr), and still got about 110.

Thanks

Les

[waterbear]

I test my TA with a Taylor 2006 kit, and it was 160 on Apr 22nd, so I lowered my PH, and run the pume with the nozzles as far up as possible. It is not doing as much airation as I would like, but I thought it would over time, running the pume 24/7. Yesterday I tested with these results:
FC 9.5
CC 0
PH 7.2
TA 110
CA 260
CYA abt 25

I have been adding Triclor to keep FC at about 19, and boost the CYA just a bit to get to abt 30.

Pool is Plaster.

My question is this... My TA tests say 110. I took some water to a new Hardware store with a computerized testing setup, just to see how we compare. Their results are:

FC 9.6
TC 9.6
CC .0
PH 7.4
CA 160
Alk w/ stabilized correction: 0
CYA 25

Why do they show 0 fro Alk, and I show 110?? She run the test 2 times??

I also came home and run a alk test with a different test kit (bought at walmart last yr), and still got about 110.

Thanks

Les

Are they using the LaMotte WaterLink Express/Datamate software system with the little vials that they inject the water in and then read them in the colorimeter? If so then I know what is happening. The TA test in that system will read low if the FC levels are 10 ppm (or in that general area). That is a documented interferance that any LaMotte certified operator would know about. Ditto for the differences in the CH and pH tests. The powdered reagents that LaMotte uses seem more prone to bleachout or interference at high chlorine levels than the liquid reagents that Taylor uses. I would suggest waiting until your FC drops a bit and then checking the test results. The LaMotte chemisty is accurate but it's little quirks do need to be taken into account (The Taylor chemistry has it's own little quirks that can give inaccurate results also!)

Edit: Also, it seems that LaMotte recently had a batch of TA unit dose vials that were not good. We had to return some to our supplier because they were all showing very low TA. The replacement ones we got did not have the problem. Once again that type of thing can happen with ANY manufacturers testing supplies.

[hooeld]

Thanks Waterbear.. That makes sense..

It was the type tester you mentioned..