Pool store test results - any confidence in them?

[scott39]

I've been lurking for about a month now.

After a horrible summer last year...algae, pool store recommended phosphate treatment, more algae, new cartridges for my filter, etc....i am now using bleach exclusively. I have some old shock, pucks, and some calcium hypo that i will still keep around if i am desperate for chlorine.

I purchased one of the recommended test kits and have been testing regularly since opening in mid-April. I took a water sample to the pool store today, more out of curiosity than anything else, to compare their results to my results.

There are two outliers: the CH from the pool store reads 205 while i get 325 from the drop test. And, the pool store shows TA (input) of 100 and TA (adjusted) of 47 while i get 80-90.

The pool store uses the ClearCare Expert computerized system.

Any experience with the differences?

Thanks. Trouble Free Pool is a great blog!!! As an engineer, it is very comforting to see the chemistry supporting the method.

 

[tim5055]

Welcome to TFP!

Always believe your testing. If those are the only two differences you hit them when they have had the machine calibrated and did a fair job.

We always like to,ask what all your testing looks like, and how does the pool look?

 

[chiefwej]

Believe your tests. Ignore the pool store results. I have tested my water then taken a sample to three pool stores and got three different results, yet my test is repeatable and consistent. The whole purpose of having a good test kit is to have dependable and reliable test results. Trust yourself and ignore the pool store.

 

[Isaac-1]

While some pool stores may be better than others when it comes to testing without your own quality test kit you can't know if yours is one of the good ones are not. More importantly just because they got the testing right today does not mean they will get it right tomorrow, even with the fancier computerized test setups, there is still plenty of room for operator error, cross contamination, etc. all before accuracy and calibration of the equipment comes into play.

Maybe one day we will see a computerized automatic tester that can compete with a quality drop based test kit, but we are not there yet. Some are however showing promise, and maybe they will get there in a few years, but as it stands even the best of them have a per test cost several times the reagent cost of the Taylor drop based kits, not even counting the up front investment issue.

 

[Divin Dave]

Right. And there likely arent very many pool store workers who can tell you the first thing about any of the science.
they could spit out a test that shows TA of 10, and not have the first clue what that might mean.

As an engineer, it is very comforting to see the chemistry supporting the method.

 

[Defgufman]

I don't bother bringing samples to the pool gods......I got me a Taylor and I BELIEVE

 

[scott39]

Thanks!

My results today are:

pH - 7.2
FC - 1.0
CC - 05
CH - 350
TA - 90
CYA - ~150
Borates - ~15

Added some bleach.

Planning to drain some water to bring the CYA down.

 

[chiefwej]

Get some chlorine in there!

 

[pooldv]

Welcome to TFP!

You are working on brewing some algae there with that low FC. FC must stay above the minimum level for your CYA level based on the Chlorine CYA Chart. Letting it drop below min is inviting algae to the pool party and then you'll have to SLAM.

CYA of 100 calls for FC of 7ppm and target of 12ppm. Problem is that your CYA is off the chart. There is a ratio but I don't know what it is, maybe target minimum FC of 10.

- - - Updated - - -

Here is some info on maintaining your pool.
TFPC for Beginners
ABC's of Pool Water Chemistry

Here are the Recommended Levels for your pool.
Here are the Recommended Pool Chemicals to maintain your pool.
Use PoolMath to determine how much to add.

 

[Patrick_B]

Welcome to the forum Scott.

Outliers like that are common. Test error, sample size, poor calibrated/maintained electronics. It's really difficult to beat tried and true Titrations for consistency.

 

[scott39]

From the Chlorine CYA Chart by Chem Geek (7.5% of CYA min % 11.5% CYA target) the min and target for 160 CYA is 12 and 18.4, respectively. Added some chlorine and ended up at 14.

Pool was great for a Mother's Day family get together.

Happy Mother's Day everyone!!!

 

[Awesemo]

I like getting my water tested at the pool store. It usually matches up exactly to what I come up with. I like having those numbers printed out on paper to look at

 

[pooldv]

From the Chlorine CYA Chart by Chem Geek (7.5% of CYA min % 11.5% CYA target) the min and target for 160 CYA is 12 and 18.4, respectively. Added some chlorine and ended up at 14.

Pool was great for a Mother's Day family get together.

Happy Mother's Day everyone!!!

Alright! Glad you figured that out! And enjoyed the pool! That is what we are all here for!

 

[Patrick_B]

E

I like getting my water tested at the pool store. It usually matches up exactly to what I come up with. I like having those numbers printed out on paper to look at.

Glad you're happy with that. Usually matching isn't good enough for us.

 

[chiefwej]

I also like having my numbers on paper to check....that's why I write them down.