High TA after adding Muriatic Acid?

[Plint]

Hi!
I'm pretty new here, but have been reading a lot of great stuff on the site. After taking my water to get tested Friday, I was told my TA was pretty high at 180. I added 16oz of Muriatic Acid with the filter running for 4hours. 2 days later I got my water tested at the same place and my TA went up to 200. I asked the guy why the TA went up and he said I wasn't running the filter long enough. Can that be possible? Am I doing something wrong or is it possible the test on Friday was done incorrectly?
Fridays Test Results
FAC 5
TAC 5
CH 590
CYA 100
TA 200
PH 8
Thanks everyone!

 

[linen]

Welcome to tfp, Plint

Muriatic acid will lower TA not raise it. Yet another reason to not trust pool store advice (or their testing). Take a look at this pool school article on test kits: http://www.troublefreepool.com/pool-school/pool_test_kit_comparison

TA testing accuracy is really only +/- 10% when it is over 100.

If you added high TA fill water between that could also explain the difference.

 

[Richard320]

Welcome!

It is probable - almost certain - that the pool store tests are wrong.

 

[Plint]

Thanks for the quick reply guys! Maybe I do need to invest in a better test kit for my own sanity.