TF-100 trouble

[TazJMT]

Hello All,

This is the first season I am using what we would call a proper test kit (TF-100). I got it a few weeks ago when I found a combined chlorine issue. Thankfully that is now taken care of.

However, I suspect there is an issue with my kit with respect to TA and CH. Here is why:
I wanted to verify my CYA results as I know that is a test that a novice can easily misread. So i got my result and then tested the water in few "non recommended" ways to see if everything was in the ballpark. First TA:

The strips I have and 2 different stores (that test 2 different ways) all have my TA between 110-120. My TF-100 test continues to give me 170 after multiple tests. I am being meticulous in counting the drops and following the directions.

Now CH:
I normally dont worry about CH very much, but since bot stores and my strips had me between 125-150 and I happen to have some CH increaser at home, I added about 5.5 lbs to my 10,000 gallon pool, which should have gotten me to approx. 200. The TF-100 has me at 400 now! I know as you read this, you assume I must be doing the test wrong, but I assure you I am not. Could I have gotten a bad/old test?

I know 1 store or strip test vs the TF-100 would have me believe the TF-100 every time, but 3 different tests agree that the TF-100 is way off. I dont know how I can trust the FC or PH readings if the other tests are so far off!

thanks

 

[Chickinvic]

I would bet that the 3 other tests are way off as opposed to the TF-100 being off (assuming you are performing the tests correctly).

 

[IceShadow]

There’s an issue with static electricity on the titrating reagent on the TA test on some kits. Try doing it again but wiping the tip between each drop and see what the result is.

 

[Flying Tivo]

Did you get the speedstir ? Those 2 test are better done with constant stirring.

 

[jblizzle]

Agreed that the SpeedStir might help here. Also the static could certainly be causing the TA to read high, are the drops hanging and falling or jumping off the tip? Finally, make sure the bottles are vertical when adding drops and not slanted.

 

[JoyfulNoise]

You’re comparing your own personal testing where you’re careful to do everything right against .... test strips???? And then two pool stores???

Strips are notoriously wrong. I can get three different brands and, honestly, get three different results. Test strips are worthless for quantitative testing.

If you’ve read for any length of time on this site (your profile says your a member since 2014) then you know how off pool store testing can be. They simply don’t care enough to test your water properly. Pool stores will often print “adjusted alkalinity” on their reports which is an unnecessary thing to do and typically causes the reported alkalinity to be 20-30ppm lower than total alkalinity.

Trust you’re own testing. Only you care enough about your pool to do it right.

 

[TazJMT]

You’re comparing your own personal testing where you’re careful to do everything right against .... test strips???? And then two pool stores???

Strips are notoriously wrong. I can get three different brands and, honestly, get three different results. Test strips are worthless for quantitative testing.

If you’ve read for any length of time on this site (your profile says your a member since 2014) then you know how off pool store testing can be. They simply don’t care enough to test your water properly. Pool stores will often print “adjusted alkalinity” on their reports which is an unnecessary thing to do and typically causes the reported alkalinity to be 20-30ppm lower than total alkalinity.

Trust you’re own testing. Only you care enough about your pool to do it right.

Yes I agree that the TF-100 is much better than each individual other test. It's just that there are so many other tests telling me that something is wrong. And I am also not seeing the issues that a very high TA or CH would show me. My water looks basically perfect (which I am grateful for) and my pH is not drifting around either, which i think i would see with a 170 TA. I'll keep an eye on it, just wanted to comment that I dont trust them more than my test, just that 3 tests telling me one thing vs my test doing another concerned me

 

[TazJMT]

Agreed that the SpeedStir might help here. Also the static could certainly be causing the TA to read high, are the drops hanging and falling or jumping off the tip? Finally, make sure the bottles are vertical when adding drops and not slanted.

The drops do hang a bit, but I have also wiped in between each drop.

However, no one has yet suggested to have the bottle vertical, I always do slant it. I will try a vertical test and see-thank you

Would the static affect the CH test also?

 

[duraleigh]

Time after time, the test methods used in the TF-100 prove themselves to be accurate....over and over and over. Test strips prove themselves to be wrong over and over and over. Pool store results prove themselves to be wrong over and over and over. You have a test kit that is as good as it gets so you must stop comparing it against inferior sources.

And I am also not seeing the issues that a very high TA or CH would show me.

I don't know what that means. a CH of 400 is at the upper end of just fine.....there is no issue to see. A TA of 170 likelwise is higher than we like but there is not necessarily an automatic visible issue with it.

1. TA - the most common cause for a TA misread is the static that develops on a VERY fresh vial of R-0009. As stated above, wipe the tip each time and holding the bottle vertically, allow the drop to fall off the tip.....don't squirt it off. The static issue is normally gone in just a week or two and you no longer have to wipe that tip until next year when you get new, fresh reagents.. If you have done ALL the above and your test result is 170, then you can take to the bank that your TA is 170

2. CH - You don't tell us what kind of pool you have....masonry or vinyl liner. We need to know that. If you are following the directions correctly, the CH test is a bit more tedious but you do NOT require the speed stir to get a good result. From your description, it sounds like you tested CH with a strip and then dosed your pool accordingly. Or, did you test CH first with the TF-100 before dosing.

Once again, if you are doing the tests correctly, you can bank on your CH being 400 and your TA being 170. You pay good money for these high end (TF-100 and K-2006C) kits and you are entitled to expect them to work correctly. Over and over, they do work correctly and you need to stop comparing them to tests that don't.

I am sure that I may come across as a little too confident in these test kits but I have been intimately involved with using them and reading the thousands upon thousands of results for 14 years or so now. These kits work.

 

[JoyfulNoise]

Titrating dispensing bottles MUST ALWAYS BE HELD VERTICALLY!!! That is a must or else you will not get the correct droplet volume (it will be too small) and you’ll get a false high reading.

 

[TazJMT]

Well-my test kit must have come with a hidden camera and you are all watching me. I just did those tests again and held the bottles vertically and the numbers came out WAY different. TA is 120 and CH is 250. Now I'm sure we all also don't want to hear that it jives with the others less accurate tests I had done, but nonetheless now I can trust the tests I am doing at home. Thanks again to everyone-I literally cannot believe it made that much of a difference. Unless I miss it somewhere, holding the bottle exactly straight up and down should be mentioned on the test kit instructions somewhere, I can not believe how much that helped!