First Test Using TF-100 / Some Thoughts & Questions


Active member
Jul 2, 2021
Vancouver, WA
Pool Size
Hi All,

I have finally tested my water myself and the results are interesting.

Honestly, they are very similar to the pool store results, so that gives me some confidence in my pool store. Actually, before ordering the test kit, I used two stores. Both produced similar results, although once in a while something seemed off. For example, last time I went to the store on Mill Plain, the CYA was 5. I knew that was wrong because CYA is cumulative (from what I understand). So the tech did a drip test and found the CYA was indeed near 50 (as I thought).

I'm going to post the results from my TF-100 test, and the results from my store test (16 hours earlier). There is one very significant difference, and that is with the calcium test, and it's a little weird, because I've gotten around 10-15 store water tests (from two different stores) and the results from this test are always similar.

Anyway, here are the results:

FC - 9.5 (I did this twice to make sure) FC - 6.1
CC - .5 (did it twice!)CC - .93
PH - 7.2 (used a meter)PH - 7.3
TA - 100 TA - 76 (adjusted) 92 (input)
CH - 450 (first test) / 525 (second test)CH - 184
CYA - 45CYA - 48

First off, a little about my pool store. They never try to sell me any chemicals (I've bought a pool and hot tub from them, so now I'm like Norm--everybody knows my name). The more I read about water chemistry, etc., from this community, the more I see mistakes in their advice, but I don't see why their tests would be off. The machine they're using is well over $1,000 and it seems to me that it should be accurate. Anyway . . .

Now, my thoughts and observations. The FC test is quite different. Not sure why.

The CC test is pretty close.

The PH test is very close.

The TA test is fairly close (the pool store uses an "input" value and an "adjusted" value - the "input" value was 96 so very close to the TF-100 results).

The CH test is wacky. I got 450 on my first test and 525 on my second test. The store results are very consistent over the last couple months. August 17 (184), August 5 (180), August 2 (165), July 26 (174), July 20 (174), July 15 (182). I've used two different stores to get those results. They are always very close and they stores are suggesting I add calcium (but my store says my calcium levels are fine because I have a vinyl pool). But they do say, "If you want to raise the calcium to recommended levels, add about 6lbs of Calcium Hardness Up." How can the CH tests be so very different?

CYA results are nearly identical so that's good.

Thank you all for getting me moving in the right direction with caring for my pool.


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
Pool Size
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Great on doing your own tests! No need to post pool store test results, we do not look at them.

Your CH is correct. Your pool is vinyl, so there is no need for calcium in the water. You just need to monitor it for scaling tendency. Does your fill water have calcium in it? Your CYA is 50, follow the FC/CYA Chart
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Gold Supporter
May 20, 2020
Katy TX
Pool Size
Liquid Chlorine
The machine they're using is well over $1,000 and it seems to me that it should be accurate. Anyway
These machines are only as good as their calibration. You do not know when or how often it is done. There is also the possibility of cross contamination from the previous customer‘s pool sample.

With regard to your CH test, be sure you are using a 10ml sample and multiply drops by 25. You can use a 25ml sample and multiple drops by 10 but that uses more reagents. You also have to put in 20 drops of 0010 and 5 drops of 0011l. For some reason, I also find that CH done by pool store is always off compared to my personal testing.
Always trust your own testing and you will continue to gain experience as you test more.
Good Luck.
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