Test discrepancy TA

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Jun 10, 2011
65
Carbondale, Illinois
I have two test kits that are giving me completely different readings on TA. My pH is consistent at 7.5 for both kits. One kit is a new TF-100 refill plus the old one from last year are both giving me a reading of 110. My pool guy's test kit that I currently have is different. Instructions say 1 drop of chlorine neutralizer, 1 drop of a blue indicator, and then 1 drop at a time of the third thing to get the result. With that test I'm getting a result of 60. With the sample he took to the shop, he says he got a result of 60.

Full set of results with the TF-100: pH 7.5, TA 110, FC 3-4, cya 70

I'm using a sand filter and SWG, but there is also a portable DE filter set up (long story). I'm not familiar with DE filters but can't imagine this causing a problem.
 
Toss the pool guys kit. That may sound flippant but it's not.

You have a known quantity in the TF-100 that you paid good money for. For that price you can expect precision and dependabillity.
 
@duraleigh that's my instinct. I really feel mine is right, but now I'm stuck with too high TA for my SWG because he added baking soda. He called me this morning and told me to add more but I didn't.

- - - Updated - - -

I ended up buying a new test kit refill because he had me convinced mine was wrong but I'm getting the same results. I don't know how old his is but he claims his is right because he calibrates it against his shop tests. His are different reagents. Goes from blue to clear.
 
We have a pool guy right now because we're doing a new construction of a pool house. I needed someone to move the plumbing and the location of the pump, and a few things like the auto vac line and the wiring to the deep end light got damaged along the way. He just lives up the road and keeps dropping in to check on things, including testing the water. He left his kit for me to use while I waited a few days for the refill to arrive after I noticed the discrepancy.
 
This is just a small hi-jack but it is certainly pertinent. Infrequently, we hear from folks worried about the uniformity of the drop size being dispensed from the dropper bottle.

The size of the hole is irrelevant to forming a repeatable and acceptable drop.

1. You must hold the dropper bottle vertically down. Do not tip it on it's side.

2. The drop does not form inside the bottle to be magically dispensed. The drop forms on the rounded outside edge of the dropper tip and, when done slowly and correctly, it finally gets heavy enough to fall off the tip. Let it fall....do not force it off by pushing the liquid out too fast.

3. A color change test is complete when the LAST drop you add makes absolutely NO COLOR CHANGE WHATSOEVER. Subtract that drop from the total and the test is complete.
 
+1 to what Dave said. You really, really have do drip slowly, let gravity pull the drop off the tip. Thanks to Dave, who gave me that advice, my test discrepancy is no more. Seriously let gravity do the work.
 

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Good news! TA of 100 or 110 is not bad. We can work that down slowly if needed as summer goes on. Sometimes high TA causes PH to rise faster, so keep an eye on it and keep PH between 7.2 and 7.8. Adding muriatic acid to lower PH will gradually lower your TA until TA and PH reach equilibrium.

Please add your pool info and location as shown here, Pool School - Getting Started, it will help us help you with better info about your pool and climate.
 
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