Ph Strip vs drop test, severe discrepancy (pic)

elc

Member
Jun 1, 2018
9
Oakley/CA
Took a Ph test of my pool with both the strip and drop test and they seem to be very different. I imagine the drop test is more accurate, but why the discrepancy? If I'm matching the color right on the drop test, it looks closest to 7.5. How would you interpret the color?

Also took the FC test with my TF100 and it took 10 drops to clear the pink fluid, which should be 5. The strip looks closer to the 10 than 5 in person.
 

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tim5055

Mod Squad
TFP Expert
LifeTime Supporter
May 11, 2014
10,479
Franklin, NC
Throw the strips away and forget about them. What you are seeing is why we call them "guess strips".

I read teh pH as 7.5 also....
 

Donldson

TFP Expert
LifeTime Supporter
In The Industry
Jun 12, 2009
3,970
NW Ohio
If test strips weren't so unreliable we wouldn't vehemently rally against their use. Despite the thoughts a few industry members (and the occasional conspiracy inclined former member) TFP is not a ploy by Taylor or TFTeskits to sell K-2006 tests. Consumer test strips are designed to be sold as cheaply as possible and that quantity over quality shows through. Since we need accurate results to offer advice, test strips are no good. Some of my favorite strip results include CYA of 50 on a fresh fill (there is no CYA in fill water) and FC of 5 and TC of 1 (TC cannot be lower than FC).

The best thing test kits can measure is gravity. Hold them exactly 9.8 meters above a trash can and watch them hit the can exactly 1 second later.
 

JamesW

TFP Expert
Mar 2, 2011
17,374
Hold them exactly 9.8 meters above a trash can and watch them hit the can exactly 1 second later.
In 1 second, the strips would only fall half way (about 4.9 meters).

The time would be 1.414 seconds to fall 9.81 meters.

The closest you can get to 1 second is on Jupiter, where the fall would take about 0.87 seconds.
 

lightmaster

TFP Guide
Jun 22, 2017
799
Baxley, GA
If test strips weren't so unreliable we wouldn't vehemently rally against their use. Despite the thoughts a few industry members (and the occasional conspiracy inclined former member) TFP is not a ploy by Taylor or TFTeskits to sell K-2006 tests. Consumer test strips are designed to be sold as cheaply as possible and that quantity over quality shows through. Since we need accurate results to offer advice, test strips are no good. Some of my favorite strip results include CYA of 50 on a fresh fill (there is no CYA in fill water) and FC of 5 and TC of 1 (TC cannot be lower than FC).

The best thing test kits can measure is gravity. Hold them exactly 9.8 meters above a trash can and watch them hit the can exactly 1 second later.
Don't forget about air resistance in a real world case. Those things are super light pieces of paper and definitely don't fall at the full acceleration of gravity.

There's no conspiracy by TFP to sell Taylor or TFTestKits, its a conspiracy by the Pool Stores to push people to Taylor. They're secretly getting paid by Taylor to increase Taylor's customer base.
 

Catanzaro

Platinum Supporter
TFP Guide
Jul 30, 2014
3,403
Monmouth County, New Jersey
One of the main bullet points in Pool School should be that no advice should be given if test strips or pool store results are provided (Bottom line). I know they are bad, but that is crazy going from a 6.2 to 7.5 (Big difference). I actually spoke to Taylor and they stated to view the vial in natural outdoor lighting. If I move the PH test away from the clouds, the color changes and it is easier for me to gauge the correct PH level.

After 4 years on the forum, anyone I know or meet with pool problems who asks for help receives the same answer.

1) You must order one of the test kits, which of course is always the TF-100 with the speed stir.
2) Join the forum

At least the first one is a must. Otherwise, I offer no advice. Just wasted time as they will go back to the pool store, get bad advice from other friends, etc.