Reasons pool store testing is inaccurate


Well-known member
May 29, 2019
Air in the container can affect pH.

If you take a sample with you to work, and have it tested after work, the results can be affected by sitting in the hot car all day.

The person behind the counter doesn't know how to do the test properly.

The person behind the counter doesn't care if the testing is done properly.

Never trust the person that is going to sell you things with your pool water testing results.

I thought a list of reasons might help some of the new posters that come here looking or help!
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Reactions: Divin Dave


Bronze Supporter
Dec 13, 2018
Orlando, FL
I found this thread after wondering why the pool store tests and my tests were so far off in some areas. It looks like they are using Taylor chemicals.

After observing the pool store do testing the reason appears that they do not really count the drops. I watched them and they just squirt a bunch of reagent in for items like TA, CH, and SALT.

Their numbers for salt are constantly about 1000ppm lower than mine. Based on their numbers, my salt cell shouldn’t even be working.

Also, the poor fluorescent lighting in the store doesn’t help.

I just bite my tongue, buy my acid, and smile as I walk out!
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Well-known member
Jul 8, 2015

Also, the poor fluorescent lighting in the store doesn’t help.

I just bite my youngest, buy my acid, and smile as I walk out!
Yuup.. These threads recreate themselves on a regular basis. I have a hole in my mouth from biting my lip...

Cholorimetry is not affected by the type of lighting. That is why its an effective method of testing in multiple environments, different sunlight, different lighting sources.

Yes they don't do a very good job of counting the drops.. they are in a rush because there are 5 more tests in the line behind you... one pool store employee told me they think their salt test is off because every customer says it doesn't match their SWG controller displays. At least he was honest.

The biggest error I see in the pool store testing (the one wth the big "L") is they do NOT rinse out the test cells before the next test. Ideally they should rinse with distilled water or at least your own water before testing. All the stores in my area are at least consistent in the error. They rinse with the last guys sample then start with the next sample. If the last guys chems were WAAAYY off it will affect the next guy who is not so far off.

Some stores tests with strips..

I always make sure to cap my sample under water. so there is no air inside.
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