accuracy of tf-100 testing

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saaej0

saaej0

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Aug 2, 2012
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San Angelo Texas
TA 150. pool store says 131
PH 7.4. pool store says 7.8
TH 700. pool store says 400
TC .9 pool store says .9
CYA 22 pool store 45

My test with tf-100 showes one thing and pool stores print out eloctronic sheet shoes another. I even tested my TA with old pool test kit i have and it matched the TF-100 kit. Being new to BBB I have been using the pool store read out to test mine because I cant get the CYA down yet. Is it normal for the pool store electronic read outs to be so far off?
 
Often the "electronic read outs" just use a test strip and match the color on the strip. They're not accurate at all.....trust your own testing! The only reading that jumps out to me is your TH reading? How many drops did you add? Is your water cloudy?? A 700ppm level of calcium is very much so in the danger zone.

As for the CYA test....check out this video. It shows the "dot" and just what it should look like once finished. As long as your levels are low (which yours are) then it's not a majorly important test to get 100% on the nose. As long as you shoot for the higher end of your FC levels you'll be fine.

CYA Test in the TF-100
 
Hi, welcome to TFP! It is not at all uncommon for your test results to differ widely from pool store results, especially if they use the computerized tests. The computerized tests have to be re-calibrated frequently to maintain any chance of accurate results. Trust your own test results. If you are unsure of a result, run the test again, and check here to see if you followed all the steps correctly.

I do have a question about your current test results. You show a result for total hardness (TH) but the TF 100 does not test TH. Did you mean CH (calcium)? If that was your calcium result, be sure you are swirling well between each drop. Adding drops too quickly will affect the result of the CH test. Also the CYA is read in increments of 5 and has an accuracy of + or - 10ppm. You mention you are trying to lower CYA, but the recommended range for CYA is 30-50ppm. The pool store result is in range and your result is not too far below range. Finally, the TF100 measures FC (free chlorine) and CC (combined chlorine). You can add FC and CC to get TC (total chlorine) but there is no TC test in the TF100. If you test FC with a 10ml sample of water your results will read in increments of .5, if you use a 25ml sample the results will read in increments of .2. If you got .9 as a result you need to run the test again. A 10ml sample will save reagents and give an accurate enough result for everyday use.

(EDIT by jblizzle to correct .02 to .2 and a couple typos since i was here ;))
 
Thanks for your help. I meant to say I was trying to get the CYA test process down, not the CYA it self. You are right my 700 is CH not TH I added 70 drops. I got my CH test once then every time I do it now I get purple and can't get any results. My water is currently a little cloudy. Even when I ad the two R0012 up front I get purple. I did order a magnetic stir today. I cant tell the difference in the yellow squares on the chlorine test tube so I did test FC=.5 and CC=2.5. per calculator I added 182 oz of 6% bleach and have not re-tested yet. I also ordered a different oto test kit witout yellow so I can read chlorine daily better. as well per leebo's response i viewed video to help me do CYA test correctly.

Thanks again
 
So your CC is 2.5? That would certainly indicate a need to start the shock process.

Can you describe how you did the test ... how many drops, etc ... So we know the test was done correctly.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
It sounds like you used the K-1000 for your chlorine test. I too find this test tuff to match, and often only use the FAS/DPD test to check my chlorine level. Try to do that test and post your results. A CC reading of 2.5 is an indication that shocking is in store.

Test your Calcium level again once you get your SpeedStir. This test is the main one that I find is MUCH MUCH easier to preform with the SpeedStir. Do you have high Calcium levels in your fill water?
 
I am testing with TF-100 Kit exactly using instructions from this site. here are my test from this morning. The CH test is from running to leslies pool center. They used a magnetic stir and same chemicals I have. They got 290 and i ran to another store using electronic reader and they got 300 so I think the 290 is good reading. I cant use my CH reading till i get my magnetic stir i orderd because i keep getting purple color at 825 for pool and 700 from well so I know thats messed up.

It was 107 degrees here yeasterday.

CYA 36
PH 7.7
FC .5
CC 4
TA 160
CH 290 from pool above
 
So your CC are even higher. Have you read the shock process in Pool School? Time to get started.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
Your right. thanks. didn,t know were my head was. I was just adding enough chlorine to bring up level up to 3. i just followed shock process and added 500 oz of bleach at 6% to bring to recommended schock level of 12.
 

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now wait an hour and retest the FC and CC and bring it back up to shock level. Repeat until you pass the three tests to stop the shock process.

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
If the FC dropped that much, you should check it sooner the next time. Are you shooting for the shock level for a CYA of 40ppm?

Posted from my Droid with Tapatalk ... sorry if my response is short ;)
 
If you're losing that much chlorine, test sooner and give the pool a tip when you dose so you won't actually fall below shock level. Go with 40ppm CYA as well, 36 is far too precise. It's 40 for all intents and purposes here, so use that shock level.
 
You're gonna love the speedstir. My CH miraculously dropped several hundred points by testing with the speedstir versus swirling by hand. :mrgreen:

When you do get the speedstir, when you hit purple, stop adding drops and just let it run. Then run it a full cycle (it has a timer) before adding any more drops. A lot of times if I'm just patient (A minute is a long long time when you're just staring at the tube) it will go blue with no extra drops.
 

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