New to TF-100... First trial showing incorrect results

lrvalley

Member
Oct 16, 2019
8
Florida
Hello all! Looking for a little help! Just put in a new pool, and am going to maintain myself. I've had a pool at other residences for nearly 35 years, so I'm familiar with pools, but this is my first gunite pool.

I started out with a Color Q Pro 7 for testing, but the test results were all over the place and highly inconsistent. I then came across the TF 100 recommended in numerous reviews, so I ordered the kit along with the SpeedStir.

I ran my first set of tests today... and while the instructions appear pretty easy to follow, my test results do not match my local pool pro store results. I have a 6,800 gallon gunite pool with a salt water chlorine generator.

Here are the readings from T&D (Pool Store), and the TF-100:

Test / T&D / TF-100
Free Chlorine / 8.8 / 14.0
Total Chlorine / 10.0 / NA
Combined Chlor / NA / 0.0
pH / 8.4 / 8.2
Alk / 90 / 200
Calcium Hardness / 353 / NA
CYA / 75 / 83

The only two tests even close are pH and CYA. The Calcium Hardness test doesn't seem to work at all... I fill the cylinder to the 10ml line, add 10 drops of R-0010 and mix, then I add 3 drops of R-0011L and mix. It turns pink. I should have had to add about 14 drops of R-0012 for 353... I stopped adding drops after 30 when there was no change.

What could I possibly be doing wrong?

Also - I know chlorine and pH are high. I have backed off my filter hours and dropped the salt cell to 5% to get chlorine levels down, and added muriatic acid to bring down the pH

Right now, I'm just concerned about getting the right test readings.

Any help would be appreciated!
 

Texas Splash

Mod Squad
TFP Expert
LifeTime Supporter
Sounds like you're doing the CH test right. I don't trust pool store tests, but if they show over 300, perhaps it's much higher? Have you added calcium or cal-hypo products in the past? Local water hard? Some people (usually out west) have a CH of 800 or more. It would be good to keep going past the red after you added the 3 drops of R-011 and keep adding the R-0012 until you reach the light/baby-blue. Results in 25ths (i.e. 250, 275, 375, 450, 500, etc)

The TA is pretty straight forward as well: 25 ML sample size, 2 drops of #7, 5 drops of #8, then a drop at a time of #9 until it turns Barbie pink and multiply by 10. Result in tenths (i.e. 120, 140, 160, etc)

Try wiping the tips of each of those new bottles a couple times to remove any static electricity. Might help.
 

tim5055

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May 11, 2014
10,415
Franklin, NC
Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing. Plus, the results of their "testing" is used to convince you that you need to buy things. Why do you think that testing is free?

I'll be honest, we will trust your results over the pool store all day.

As to your CYA, don't equate “just a little over” to a number, the tube is not marked for such extrapolation. Always round up to the next number. So, your CYA is 90.

With a CYA of 90, your chlorine is rally not that high. It's safe to swim up to the SLAM level, so no problems there.

Your CYA is just a little over what we would like to see, so with splash out and filter cleaning it will come down.

Witha CYA of 90 we say teh absolute minimum your FC should ever be is 5 and to make sure it is always there you should target 7.

See this for more information.
 

duraleigh

Admin
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Apr 1, 2007
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Welcome to the forum:wave:
my test results do not match my local pool pro store results.
At least nine out of 10 times the pool store is wrong. That's why you purchased the TF-100 to begin with.....so you can trust your own testing.
 

lrvalley

Member
Oct 16, 2019
8
Florida
Added Muriatic Acid yesterday to lower pH - and got the solution to turn for hardness. New readings are as follows:

Free Chlorine 14 (still hasn't changed - going to turn off salt cell for a day or two)
Combined Chlor 0
pH 8.0
Alk 170
Calcium Hardness 625

With regards to the hardness - I'm a little surprised at the TF-100 reading. I tested my tap water, and it's around 100 - the same water that was used to fill the pool. Two different pool stores came in at 338 and 353 (one used a BioGuard system, the other used standard chemicals), and my Color Q came in at 295. All on the same sample. Can all 3 of these really be off by a factor of 2? If it really is 625, should I be concerned? This is a new pool - it's had water in it for about 6 weeks now.

One concern I have is that to maintain my Wet Edge warranty, I need a record of a "Professional" water test once a month. If the results from the pool store are way off the actual values I am getting, that may cause an issue if I ever have to submit a warranty claim. Thoughts?

Thanks for all the help!
 
Last edited:

YippeeSkippy

Mod Squad
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Jan 17, 2012
11,668
Evans, Georgia
When I do the CH test I use the older test directions- 25mL of pool water in the vial. 20 drops of R-0010 and mix. Then add 5 drops of R-0011 and mix. Then add the R-0012 one drop at a time and count them till the solution turns grayish blue and additional drops don't change the sample any further. Then multiply by 20 to get your result. (example, 18 drops til blue would be 360ppm of CH)
Humor me....Please try this and see if your results are any better?

Maddie :flower:
 

lrvalley

Member
Oct 16, 2019
8
Florida
I haven't used any shock products as of yet, but would not use a calcium containing one when I do.

Trying the older instructions, I get about the same reading - 600.
 

wireform

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In The Industry
Aug 15, 2017
496
Spring Valley, NY
Don't know why nobody mentioned it but with the FC over 10 you won't get an accurate PH reading. You'll have to wait till the FC gets under 10 to see where the PH really is at.
 

duraleigh

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Apr 1, 2007
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Sebring, Florida
Don't know why nobody mentioned it but with the FC over 10 you won't get an accurate PH reading.
Well, it's not over 10 ppm....it's 10 ppm. Also, it's not like at 11 ppm FC the pH suddenly, wildly goes askew, it will simply BEGIN to read a little high. A little higher at 12 ppm and a little higher at 16 ppm and so on. The error is small around 10 ppm and increases slowly as FC goes up.

Given the subjective nature of the pH test to begin with, an FC of around 10 ppm will give an accurate result.
 
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tim5055

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May 11, 2014
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Franklin, NC
Well, it's not over 10 ppm....it's 10 ppm. Also, it's not like at 11 ppm FC the pH suddenly, wildly goes askew, it will simply BEGIN to read a little high. A little higher at 12 ppm and a little higher at 16 ppm and so on. The error is small around 10 ppm and increases slowly as FC goes up.

Given the subjective nature of the pH test to begin with, an FC of around 10 ppm will give an accurate result.
The 10 was the Pool Store total chlorine number. The TF-100 was at 14 FC. Still not a huge amount above 10, but above...