Test Kits and Accuracy - Whom to Believe

[ComputerGuyInNOLA]

Billrector,

I had a Safedip electronic tester that had to be calibrated monthly to a standard solution for PH according to the instructions. Not only that but the sensor had to be kept moist at all times. The sensor had a rubber boot with a small sponge in it. What a PITA! I believe all PH testers must be calibrated this way although I could be wrong. After using it for three months I sold it on ebay. I paid $140 for it and got $12 for it at auction. Lesson learned.

 

[Bama Rambler]

Some things require more frequent calibration than others. As Computer Guy mentioned pH is one of those instruments that require frequent calibration or it becomes completely useless.

And for the record, I have my multimeter calibrated to a NIST standard every year. While that's overkill for the vast majority of folks, it's required for me.

While I don't believe that normal pool care requires extremely accurate testing you need to at least check the testing method periodically to make sure it's at least close to the real world.

 

[chem geek]

Some chemical measuring devices are finicky and need regular calibration. pH and ORP most definitely need regular cleaning or calibration to be accurate. As for photometric tests, they typically just need to use a clear reference cell as a baseline, but the inaccuracy can come in from the chemistry of what is being measured. For the FC test, if DPD is used then it bleaches out at higher levels so becomes less accurate from 5 to 10 ppm and generally not accurate at all above 10 ppm FC. The colorimetrically-based TA and CH tests use chemistry that can have interference that is different than the drop-based tests and generally higher CH levels aren't measured well. In theory, the turbidimetric test for CYA should be easy to get right, but in practice those results have been seen to be flaky, though even the visual test is difficult in this case.

Basically, some of the colorimetric tests are not much better than using test strips. Titration tends to be more accurate than absolute colorimetry for some tests because of the type of chemistry that is involved.

So while not all electronic instruments need regular calibration for reasonable accuracy, we aren't talking about simple tests and measurements here. We're talking chemistry where colorimetry is different than drop-based titration chemistry.

 

[johnsimion]

Hi, I have the following information about my pool, I just can't figure out how to add it to my signature! I put some stuff in my profile but couldn't find anything about the signature -- not sufficiently computer literate. Help?
The size of your pool in gallons: 19,000
If your pool is an AG (above ground) or IG (in ground): IG
If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass: Pebble-Tech
The type of filter you have (sand, DE, cartridge) and, if you know, the brand and model of the filter: Cartridge, Pentair (big - has three cartridges inside it)
If you know, please tell us the brand and model of the pump, and mention if is it a two speed or variable speed pump: Pentair variable speed pump
Date of pool build/install, particularly important if less then a year old: Completed and running in February 2014 (i.e., six months ago)
What kind/model of water test kit you are using: LaMotte 2056 ColorQ Pro 7
Other significant accessories or options, such as a spa , SWG, or cleaner: Solar heat, waterfall, spa with a spillover and gas heater, water softener for the feed line, and an in-floor popup system that works but isn't necessarily effective at removing all the desert dust, so I also use an electric robot cleaner that works great.

Today they are draining my pool and beadblasting out the calcium. Tomorrow they re-seal my boulders with a good quality sealer that should last more than six months (!) and then I'll be ready to refill and start over.

 

[JVTrain]

Hi, I have the following information about my pool, I just can't figure out how to add it to my signature! I put some stuff in my profile but couldn't find anything about the signature -- not sufficiently computer literate. Help?
The size of your pool in gallons: 19,000
If your pool is an AG (above ground) or IG (in ground): IG
If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass: Pebble-Tech
The type of filter you have (sand, DE, cartridge) and, if you know, the brand and model of the filter: Cartridge, Pentair (big - has three cartridges inside it)
If you know, please tell us the brand and model of the pump, and mention if is it a two speed or variable speed pump: Pentair variable speed pump
Date of pool build/install, particularly important if less then a year old: Completed and running in February 2014 (i.e., six months ago)
What kind/model of water test kit you are using: LaMotte 2056 ColorQ Pro 7
Other significant accessories or options, such as a spa , SWG, or cleaner: Solar heat, waterfall, spa with a spillover and gas heater, water softener for the feed line, and an in-floor popup system that works but isn't necessarily effective at removing all the desert dust, so I also use an electric robot cleaner that works great.

Today they are draining my pool and beadblasting out the calcium. Tomorrow they re-seal my boulders with a good quality sealer that should last more than six months (!) and then I'll be ready to refill and start over.

Click on the Settings link in the upper right of the screen. Then click on the Edit Signature on the left side of the resulting screen. Dump your details in a similar fashion as other users here.

 

[MoebiusStreet]

The Taylor and TF 100 tests change color. Example when you do TA test, the color changes from Blue Green to Red. ... There is no doubt such as the types of tests where you have to compare shades of the same color.

I have to disagree here. The other tests, for chlorine, etc., are great. But for TA there's plenty of room for misinterpretation. As you say, it changes from blue green to red. But it does so by traveling through purple. At least as I experience it, there's a pretty broad judgment call from "blue-ish purple" to "red-ish purple" to "pretty much red".

 

[RobbieH]

There isn't. Because you keep adding drops until the color stops changing. For me it is very easy to tell when it stops. So lets say you add 8 drops, then when you add the 9th it stays pink (or red, whatever you prefer to call it) with absolutely no change in color at all. TA = 80.

 

[JVTrain]

There isn't. Because you keep adding drops until the color stops changing. For me it is very easy to tell when it stops. So lets say you add 8 drops, then when you add the 9th it stays pink (or red, whatever you prefer to call it) with absolutely no change in color at all. TA = 80.

+1

Check out the Extended Test Kit Directions In several locations it states:
Continue adding drops as long as the color continues changing. The final drop, that does not change the color any further, does not count.

It's a well defined endpoint.

 

[chem geek]

I want to refer again to my earlier post in this thread that references standard solutions you can use to see how accurate the tests are. You can then compare test strips to photometers to visual drop-based tests.