TF100 calcium hardness test

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dscassel

0
May 31, 2016
7
Gilbert
I recently bought the TF100 test kit and have been having trouble with the CH test. When I test it, my sample never turns from red to blue even after going as high as 50 drops of R-0012. At first I though that my calcium levels were through the roof but then I took a sample to Leslie's and it was reading ~400ppm. So then I thought that maybe the test kit chems were contaminated but when I tested our tap water they seemed to be at normal levels for Arizona water (~300ppm).
My water analysis report from Leslie's read as follows:
FC: 7.5 ppm
TAC: 7.5 ppm
salt: 3600 ppm
CH: 400 ppm
CYA: 90 ppm
TA: 120 ppm
pH: 7.8
phosphates: 200 ppb

I know some of these are a little on the high side but can any of them cause an issue with getting a proper reading with the CH test?

Also to note, I recently converted to a salt pool a few weeks ago if that may have something to do with it.

Thanks!
 
Hello and welcome to TFP! :wave: We all know AZ has some of the hardest water out there. With tap water at 300, you can imagine how refills to the pool would send it up higher because CH doesn't just go away. 50 drops is about 1250 ppm, and we've seen that before. By any chance are you mixing with a speed stir? Those are extremely beneficial and have been know to provide better results when testing CH.
 
Help us by being very specific. What size sample are you using? The TF-100 instructions call for a 25 ml sample unless you have a pretty old kit. Let's get you tuned in on how you are performing the test.

I will tell you this, if we get the sample size and drop count correct, I'll put my money on your results opposed to Leslie's
 
I just purchased the test kit a few weeks ago (May 8). I am using 10mL per the instructions, adding 10 drops of R-0010 followed by 3 drops of R-0011L. Also, I am seeing very little scaling at the water line where I would expect more if I were at 1250 pm.
 
Hi dscassel :wave:

Welcome to TFP from a fellow Arizonan (I'm down in Tucson). I'm willing to bet your water hardness is A LOT higher than you think it is. My water started out at ~300ppm CH and, after 3 years or so, is now at 850ppm CH. If you leave your pool uncovered, evaporation in Arizona is ENORMOUS! In Mesa, pan evaporation data shows about 94" per year of water loss. In Tempe, it's about 74" per year. So let's say for Gilbert (not on the list of pan evaporation sites in AZ) you're about in the middle, ~84" per year; that means an uncovered pool will evaporate 7 feet of water per year. How deep is your pool? When was the last time you exchanged your water with fresh water? Your tap water is a lot like mine, ~300pm CH. So, if your pool is about 7 ft deep (pretty standard in AZ) you could expect your CH to increase by somewhere near 300ppm every year (in an uncovered pool).

My guess is you're just not adding enough drops. But, to be sure, try this -

Use a 10-mL water sample
Add about 10 drops of R-0012 first.
Then add 10 drops of the R-0010.
Next, add about 4 drops of R-0011L to make the intensity of the color a little stronger.
Finally, keep adding R-0012 drops until you see the color change.

Add up all of your drops of R-0012 and multiply by 25ppm/drop.

See what you get.....
 
Matt,
I'll try this but also note that I had just filled the pool last July so less than a year ago. Other neighbors I've talked to have values less than 400 ppm and have not changed their wafer in well over a year, maybe two.
 
dscassel said:
Matt,
I'll try this but also note that I had just filled the pool last July so less than a year ago. Other neighbors I've talked to have values less than 400 ppm and have not changed their wafer in well over a year, maybe two.
Click to expand...

OK. Well, the variation to the instructions I offered is what's called a "fading endpoint" test. Sometimes the CH test is affected by metals in the water of if there are other hardness species (like magnesium) present in excess of what the R-0010 would neutralize. The number of R-0012 drops added BEFORE the R-0010 is not critical; I typically try to add about half the number of drops I think I'll need. Also, you can add an extra drop or two of the R-0011L indicator dye to increase the color intensity of the water sample...I find that 3 drops is just to weak to see. Also, try to do the test outdoors if you can with bright, indirect sunlight. I have tried doing the CH test indoors and it just doesn't work well for me.

As far as evaporation and CH goes, if your neighbors are using solar covers, that helps A LOT! I just started using a solar cover myself because I got tired of paying HUGE water bills every summer...based on Tucson pan evaporation data, my uncovered pool (if I did not have an autofill) would completely evaporate in about a year. So every year that I operated it uncovered, I basically added the average amount of my tap water CH to the pool, which for me is about 300ppm.

Good luck.
 

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Matt,
So it looks like adding a couple of extra drops of R-0011L helped a lot. 27 drops of R-0012 is what I counted which equates to 675 ppm which is a much more likely reading. Do these extra drops of R-0011L change the multiplier at all?
 
Nope. The R-0011L is just an indicator dye that reacts to the calcium in your water and turns pinkish-red. The titrant (R-0012) is a mixture of EDTA and a stabilizer which strips the calcium away from the dye causing it to turn from pinkish-red to purple to blue. Adding an additional drop just improved the color intensity a bit but doesn't change the overall transition point.
 
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