Variations in commercial analysis

[r37890]

We recently had a pool installed in our backyard and the builder stated that we needed to bring a water sample by their office once a week for the first four weeks for (free) analysis. As I had already found this site and purchased a TF100 Test Kit prior to the completion of construction, I was interested in any deltas between their numbers and my own. The builder was using the BioGuard Accu-Scan system, but has recently switched to the newer BioGuard scanning system that does not use any strips.

To make things really interesting, I also had Leslie's Pool Supply test the water as well. All tests came from the same bottle of water.

• 
  Test . . TF100 . . BioGuard . . Leslie's
  FC . . . . 3.5 . . . . . . 2 . . . . . . 4
  CC . . . . . 0 . . . . . . 0 . . . . . . 0
  TC . . . . 3.5 . . . . . . 2 . . . . . . 4
  
  TA . . . 140 . . . . . 152 . . . . . 130
  CH . . . 180 . . . . . 182 . . . . . 150
  CYA . . . 70 . . . . . 120 . . . . . 50
  pH . . . 7.8 . . . . . 8.4 . . . . . . 8.0
  T . . . . 76° . . . . . 76° . . . . . 76°

Obviously my pH was too high and I have since fixed that (pH = 7.2). But what concerns me most is the variation in the CYA levels as the only way to lower this number is by drain/refill. The measured CYA levels have been constant for both the TF100 and BioGuard for the past 3 weeks. While I am technically a 'newbie' at this, I am not totally ignorant about all this as my degrees are in Chemistry. I even asked about the GRR and calibration method used for the BioGuard system, but all I got was a blank stare.

So does anyone on this site have any info on how the new BioGuard system works? Any accuracy numbers? I'm assuming it is spectrophotometric as the sample spun and all test are performed simultaneously. I would really like to know if my CYA is really 120.

Ron
PS Sorry about the table, but I haven't found the code to change the font to fixed width.

 

[Bama Rambler]

Welcome to TFP.

First and foremost, trust your own testing! If you read around on this site a bit you'll soon learn how consistantly bad pool store tests are. It doesn't matter which system they use, one is no better than another. You'll also begin to see that they are the most wrong on the CYA test.

I would fully trust the results you get with the TF-100.
I would also not change a parameter based on their testing unless it creates an warranty issue with them.

 

[jblizzle]

Welcome to TFP!!!

I even asked about the GRR and calibration method used for the BioGuard system, but all I got was a blank stare.

I think this pretty much answers your question. They do not have a CLUE how the machine works or how to maintain it ... so why would you trust its output?

Trust your own test kit and hopefully it will not cause warranty issues as Dave said.

 

[chem geek]

If you were concerned about accuracy of any of the tests or if you wanted to prove to the others that their tests are wrong, you can always get standard solutions for 50 ppm CYA, 100 ppm TA and 200 ppm CH.

 

[Patrick_B]

Trust the kit you have. Use it and forget the rest. I use the best Photospectrometers made on a near daily basis, and they do not rely on simultaneous analysis at all. I would never trust one that did either. Did they say you had to bring water to them for warranty purposes or something similar?

 

[Isaac-1]

One follow up note here, lighting conditions are critical to good results on the TF-100 CYA test, this test should be done outdoors in bright light (full sun light) with the sun to your back and view tube held at waist level.

Ike

 

[r37890]

Trust the kit you have. Use it and forget the rest. I use the best Photospectrometers made on a near daily basis, and they do not rely on simultaneous analysis at all. I would never trust one that did either. Did they say you had to bring water to them for warranty purposes or something similar?

I say simultaneous, but in reality it is a chambered plastic wheel. The counter person injects the water in the center, then places the wheel in the detector. The wheel is spun which forces the water into a number of small chambers along the circumference of the wheel. I'm assuming each of these chambers is equipped with the appropriate chemicals for an individual test.

While they don't mention the warranty specifically, the start up instructions do say that I need to bring water in for analysis weekly for the first four weeks. So I figure why give them an excuse later on down the road. With an investment this large I'm thinking a little paranoia is a good thing.

But since both the vendor and Leslie's have in common is that they are using this as an opportunity to sell something. Leslie's recommends (and tests for) phosphates in the ppb level. And, of course, have something for sale to 'fix' your high counts. I guess they don't realize that this just increases my doubt of the veracity of their test.

 

[Safetybob]

First, thanks for posting the results of your testing versus the other two. I was suprised that they were all as close as they were.

If your not already, keep the results of your testing (and maybe their's too) on a spreadsheet. If there is a problem and they claim you weren't doing your job, you have the evidence that "speaking as a chemist" shows their testing proceedures and calibration issues leave doubt as to their accuracy, not yours. Like you said, with an investment as large as you shelled out, showing the next home owner your documentation that the pool is good and no problem would be icing on the cake for a potential sale. For now, that testing documentation will expose any change that might be occurring that needs attention.

Be glad you found this site when you did. There is so much good, useful info here for the new pool owner.

Bob E.

 

[Isaac-1]

....But since both the vendor and Leslie's have in common is that they are using this as an opportunity to sell something. Leslie's recommends (and tests for) phosphates in the ppb level. And, of course, have something for sale to 'fix' your high counts. I guess they don't realize that this just increases my doubt of the veracity of their test.

You are not their typical intended audience.

Ike

 

[linen]

You are not their typical intended audience.

Yes, you are supposed to ohh and ahh...then reach for you wallet

 

[Patrick_B]

You are not their typical intended audience.

Yes, you are supposed to ohh and ahh...then reach for you wallet

:lol: :lol: :lol:

Very funny guys, but oh so true!