Recommended TF-100 test results: Art or Science?

BowserB

Silver Supporter
Jul 29, 2018
386
Katy, Texas
I have a laminated instruction card that came with my TF-100 kit. Now I'm see contradictory information. Two items, plus a small clarification.

* Calcium Hardness. Instructions on my laminated card say use a 10ml sample and that a result of 250-400ppm is ideal. Now I've read on this forum that new recommendations are 350-500ppm. That's quite a difference, especially if you were normally near the low end of the ideal range. At tftestkits.net I still see 250-400ppm as ideal. Also I'm reading on the forums that I should do this test with 25ml of pool water and correspondingly different numbers of reagent drops.

* Total Alkalinity. Instruction sheet says 60-90 for salt pools and 100-120 for manually chlorinated pools. Now looking at instructions at the tftestkits.net website, I see "70-120 generally works well" with none of the original salt pool and manually chlorinated pool reference. And I'm also seeing recommendations in the forums of TA of 50-60 to control pH rise.

Another minor point. Taylor specifies for the drop test either two level scoops or a heaping scoop. Responding to an inquiry here a couple weeks ago about inconsistent results from the drop test, I did my own semi-scientific testing and found that if I didn't use "plenty" of powder, I could get a false low reading. I use the SpeedStir mixing device--which I highly recommend! In the end, I reached the conclusion that if I had some undissolved powder after thorough mixing, I could count on consistent results. Too much powder wastes powder but does not adversely affect the outcome. Too little OTOH could give a false low result. FWIW.
 

Newdude

Gold Supporter
TFP Guide
Jun 16, 2019
5,471
NY
You are spot on with the powder and I've seen it myself after getting stingy with the 'heaping scoop.' Now I look for a small amount that didnt dissolve before I start drops.

The TA can be happy from 60 to somewhere in the low to mid 100s. It only needs adjusting if the PH is swinging wildly. If the PH is stable the TA is fine.

I can't help with CH for your plaster because I have a vinyl pool that supposedly doesn't matter. I have found however that my thick liner likes it to be over 150 or it seems to loose its pliability and get very tight/stiff. A few years ago it was pulling out of the liner track in several places and at the advice of a PB (before TFP) i added calcium which wasn't my normal concern and it seemed to solve the stiffness. I also have wondered about the vast difference in ranges and find it comical that for all the precision in the other tests, calcium is. 'Meh, 250- 500 is fine'.
 

YippeeSkippy

Mod Squad
LifeTime Supporter
Jan 17, 2012
15,178
Evans, Georgia
After long consideration and review with a plaster/cement expert (OnBalance) and chemistry gurus TFP updated some of their recommendations on chemistry levels recently.

Your card isn't *wrong* per se, we've just extended the range a bit. It shows that TFP continues to base the method on the most up to date information and allows for evolution.

Maddie
 
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