Measurement Error (Shelf Life of TFT-100 Test Kit)?????

[mmcwhorter]

I opened the pool a few weeks ago and the pool water has been under +60F for some time, so I balanced the pool and didn't worry too much about adding FC, especially since bleach it a bit tough to find right now. We so far only just use the spa and when I kick it on, I add a few ounces of Bleach to the closed-loop spa water while waiting for the temps to come up. Usually up to about 3-4 ppm.

Recently, the pool water hit 65 and I decided to SLAM before installing mt SWCG. I measured the pool before SLAM and got:
FC=0
CC=0
PH=7.3
TA=75
CYA=39
CH=380
SALT=3100

My CSI was 0!!!!! I don't think THAT has ever happened before.
(these measurements from the Pool store. my TFT-100 kit is much in agreement)

SLAM chart says get FC=16 with CYA = 40. Pool math says to add 4 pounds 4 oz of Cal Hypo to get to 16ppm from 0 ppm. At sundown, I added 2 pounds, waited 30 min, added two more. It was all very well dissolved in a 5-gallon bucket before slowly adding to the pool.

I waited a couple of hours with filter running and at 10 PM measured FC using the CL Drop Test method for OCLT and got 24ppm. I was a bit surprised it was so high.

I have always thought my pool was 23,000 gallons. In fact, when we drained it for an acid wash 3 years ago, I paid for the trucks to deliver the replenishment water so I didn't crash my well....and I recall this was the amount required to fill the pool.

So, I know Pool Math is correct, and it leads me to believe my R00870/1 may have a shelf life expiration issue... I have no idea how old these reagents are. I bought a refill once. Probably two years ago. I really don't know if the reagents I used are from the refill or the original kit form 4 years ago.

Bottom Line: Can anyone advise on the shelf life of the R0870/1 items int he TFT-100 test kit?

 

[Texas Splash]

My CSI was 0!!!!! I don't think THAT has ever happened before.

I got that result about a week ago myself. Made me look twice.

As for the drops & powder, I would order a new batch from HERE. A batch can last about one season and that's it. Some other things you mentioned though:
- I would avoid anymore cal-hypo. Not only is it not the best item to use for a SLAM, but your CH level is already high enough. Even if you exchange water in your area from rain and winter, you don't need it too high. Stick to liquid chlorine/regular bleach for best results.
- In the future, just post your own TF-100 test results. Whenever you mention pool store testing the hairs stand-up on the back of our necks.
- Are you using a speedstir? It sure makes a big difference, especially for teh CH test.

 

[mmcwhorter]

Thanks, TS...

The ONLY reason I went to the pool store for the test was I did not know at the time I was completely out of CYA reagent. All of their numbers matched my TFT-100 test kit for all the other parameters. So I did use both methods (except CYA) and all in agreement. Since a requirement to SLAM is knowing CYA, I had no better alternative. Plus, their salt test has been proven for three years to be accurate (at least in agreement with my low salt indicator light on the IC-40). I have since ordered a new CYA reagent. Didn't even think about the R0870/1...I guess I'll have to get some.

I do not use speed-stir, and I noticed that it took a good 15-20 seconds for the pink/red color to get really super dark after the powder dropped into the 10 mL vial of test water. I just kept swirling and it got super dark pink. I just assumed it was because of cold water. We had +33F here yesterday AM, and about +42 today.

I am aware of the CH issue. We live out in the sticks...I just can't find any bleach.

Happy to say that my OCLT was from 24 to 22. When I opened the pool last month, the water was perfectly clear, except for the leaves!!!! I assume even if the reagents are old, the difference from 24 to 22 is real. Just not the absolute number. I measured both numbers twice...as I always do.

 

[Texas Splash]

Okay, those are good things to know. Interesting about the CH test experience., Just make sure to go to the final end-point of light baby blue color. The bleach .... yes ,,,, that is unfortunate, Lastly, for the Overnight Chlorine Loss Test, when you get your new powder & drops, you might consider doing that again. You lost more than the allowable limit (24 to 22), but that could be for any number of reason right now. Re-validating with fresh reagents would be a good idea. Have a nice weekend.