Confused about Test Results

[LFreed]

New to the TFP and this forum, so "HI" first of all. I've been enjoying reading and learning what's here - excellent stuff!

My conundrum is this: I've recently purchased the TF100 test kit, and my wife and I have been carefully testing our pool water to get it back in balance after a lengthy vacation. I had been getting testing done at the local pool companies. Because I had been getting different advice from each of the different places, I decided to compare the test results between the various systems, so I took 4 samples at the same time and had them all tested within a 90 minute period (yes, I did a bunch of running around to pool companies that morning).

Here are the test results:

SunGuard: pH: 7.4, TA: 108, CH: 270, CYA: 75, FC: 0, CC: .3, TC: .3
Leslie's: pH: 7.6, TA: 160, CH: 180, CYA: 80, FC: 0, CC: 0, TC: 0
BioGuard: pH: 7.5, TA: 173, CH: 192, CYA: 117, FC: 0, CC: .3, TC: .3
TF100: pH: 7.4, TA: 220, CH: 325, CYA: 70, FC: .5, CC: .5, TC: 1.0

FC was zero (we clearly have combined chlorine, as we couldn't hold it overnight). All 4 tests were very close to each other.

pH tests were also comparable, yet the TF100 visual pH test seems somewhat subjective. Any recommendations on how to accurately determine pH?

TA and CH were all over the map. The TF100 give the highest readings of both by far. We did the tests 3 times to be sure we were exact in our measurements, drop sizes, etc., and kept getting the same results.

CYA is also pretty subjective. Even using the 50ppm sample pool water in the TF100 kit we could clearly still see the black dot at the 50ppm mark. Not sure how accurate our readings are when the black dot truly "disappears."

Any thoughts or ideas why the TA and CH are so widely divergent between the 4 tests, and why the TF100 is consistently so much higher than the rest?

Any other advice is greatly appreciated. We've had cloudy water since we got back, though we are finally able to hold chlorine. I'm running an overnight drop test again tonight to see how well it's holding (we're keeping our fingers crossed on this one .

Thanks for any insights you can provide. It's great to be a newbie on the forum.

Larry

 

[pooldv]

Welcome to TFP!

Trust your test results. We have seen thousands of times that pool store testing is inconsistent and unreliable. So much that we don't even want to know what they say.

Did you follow the instructions for the TA test? For some reason people don't sometimes and they get a false high test result.

More detailed test instructions here, Pool School - Extended Test Kit Directions. Review TA and CH to make sure you are performing the test correctly.

Have you done some reading in Pool School? ABCs of Pool Water Chemistry

Cloudy water is a usually bacteria and algae. This is because your chlorine is too low. You can do the Overnight Chlorine Loss Test to verify that organic matter is growing in your pool. If the pool fails the test then follow this process, SLAM Process

Going forward it is important to keep your FC above minimum for your CYA at all times to keep the pool safe, sanitary and algae free. [FC/CYA][/FC/CYA]

 

[duraleigh]

There is an anomaly with the TA test for the first couple of weeks that can cause the TA test (only the TA test) to read falsely high. Are you familiar with the work-around?

Other than that, like pooldv, I seldom even read pool store results......they are usually just not reliable.

 

[lightingguy]

In the Sunguard and Bio Guard test results you can see signs of a computer reader : CYA 117, TA 108. They dip a test strip in your water and put that strip into a computer reader. The computer spits out some very official looking numbers.

The problem is they are pure garbage - which your test sequence shows convincing proof of. If the stores were doing accurate testing - you would see comparable numbers.

Trust your own testing.

The only thing "wrong" with your pool right now is lack of chlorine. Check out all the articles pooldv posted - and SLAM the pool.

Expect it to take a least a few days of slamming to truly oxidize all the organics in the water - at least another few days of brushing/vacuuming to get all the algea dust out of the water. After that - keep the FC at the appropriate level for your CYA and you wont have algae problems.

Your PH/TA/CH levels look fine. Your high TA may cause your PH to rise over time - but it's not an issue to worry about.

 

[LFreed]

Excellent. I'll trust the tests.

I started SLAMing Friday after these tests were done and ran an overnight chlorine loss test each night/morning. This morning it's still holding pretty high, though it did drop some. I'll stay on the SLAMing cycle until we get it all.

Thanks for the quick responses and good advice.

 

[Teald024]

There is an anomaly with the TA test for the first couple of weeks that can cause the TA test (only the TA test) to read falsely high. Are you familiar with the work-around?

Other than that, like pooldv, I seldom even read pool store results......they are usually just not reliable.

Dave, care to elaborate on this TA test issue? What is the issue and what is the work-around?

 

[Isaac-1]

On the topic of the pH test, it can help to hold the comparator block up to a white background, also note a great deal of precision is not needed on this test since you have a fairly wide acceptable pH range of 7.2 - 7.8

 

[singingpond]

Dave, care to elaborate on this TA test issue? What is the issue and what is the work-around?

From a previous post by duraleigh:

QUOTE
When the R-0009 reagent (that's the one where you count the drops) is brand new, there is a static charge that develops between the bottle and the reagent itself. That static can skew your results too high.

The static causes the drop to "jump" off the bottle before it is fully formed........resulting in a smaller drop.....resulting in a higher TA result.

Re-do the test and, this time, wipe the dropper tip with a damp cloth in between drops to eliminate the static.
END QUOTE