Guardex Test Kit says not to perform TA test when FC is high

IslandPool · **Joined:** November 13th, 2009, 4:33 pm **Posts:** 97

in fact they say not to test for pH but I still get a reading.

still no reading on the TA happening. just nothing happening. I will test anyway again tomorrow and see if I can get a result.

is it normal not to get a TA result when FC is really high?

Thanks.

zea3 · Posted: November 17th, 2009, 11:39 pm

When FC is high it can bleach out the red reagent so you don't get a green to red color change.

IslandPool · **Joined:** November 13th, 2009, 4:33 pm **Posts:** 97

zea3 wrote:

When FC is high it can bleach out the red reagent so you don't get a green to red color change.

ah I see. Thanks. makes sense. but pH tests ok.

polyvue · Posted: November 18th, 2009, 12:57 am

IslandPool wrote:

in fact they say not to test for pH but I still get a reading.

still no reading on the TA happening. just nothing happening. I will test anyway again tomorrow and see if I can get a result.

is it normal not to get a TA result when FC is really high?

Chlorine must be really high for it to affect the pH reading so much that it becomes useless. I've been able to get nearly correct readings at 10 ppm FC and above, but it's always better to test before shocking and not rely on pH tests done when the chlorine level is over 10 ppm or climbing.

Though I haven't had issues with the Total Alkalinity test, zea3 has identified the problem. Here's what the #1 maker of test reagents says about this.

Quote:

4. When I add my total alkalinity reagent I get a yellow endpoint instead of a red endpoint. Has the indicator gone bad?

Possibly. Outdated total alkalinity indicator can cause this problem as can excess chlorine in the sample. If in doubt about the potency of the reagent, replace it. When a high level of chlorine is present, add an extra drop of thiosulfate reagent to the sample to remove the chlorine interference then follow the test procedure as written. If your water sample contains a biguanide (PHMB) sanitizer like BaquacilÂ® the alkalinity titration will properly go from green to purple instead of the usual green to red.

Source: http://www.taylortechnologies.com/Chemi ... ntentID=35

PaulR · Posted: November 18th, 2009, 1:03 am

polyvue wrote:

Chlorine must be really high for it to affect the pH reading so much that it becomes useless. I've been able to get nearly correct readings at 10 ppm FC and above, but it's always better to test before shocking and not rely on pH tests done when the chlorine level is over 10 ppm or climbing.

I believe Taylor's position on the pH test is that it should be correct up to 10ppm FC, and gradually degrades above that, and by around 15ppm you should not trust it. Adding thiosulfate to the pH test will not help, because the thiosulfate will itself affect the pH.
--paulr

IslandPool · **Joined:** November 13th, 2009, 4:33 pm **Posts:** 97

Thanks. That's a really good tip. much appreciated! I will try that with the TA test.

Tomorrow I'm diluting the FC test tube with untreated water 1:1 and then x2 to get a better FC reading. actually to get a reading period! :lol:

also buying a CYA test strip to see where my CYA is.

so hopefully I'll have readings for:

FC, pH, TA and CYA

I just have pH: 7.8

water looks great...blue and clear but I'm still brushing those black stains. And it's a painted pool.

frustratedpoolmom · Posted: November 18th, 2009, 9:15 am

The CYA Tests on the strips are the most inaccurate of all tests on the test strips. The CYA Test is virtually worthless. Do not rely on strips, except for borates and Salt.

IslandPool · **Joined:** November 13th, 2009, 4:33 pm **Posts:** 97

frustratedpoolmom wrote:

The CYA Tests on the strips are the most inaccurate of all tests on the test strips. The CYA Test is virtually worthless. Do not rely on strips, except for borates and Salt.

I don't have a choice. I can't get a decent test kit in until 2 weeks time. or should I just assume CYA is high?

Guardex Test Kit says not to perform TA test when FC is high

Who is online