Liquid Testing Vs Strips

[djmatte]

I've used strips in my hot tub since I started using it. I know a lot of people here advocate for liquid, but I just didn't see the kits here for sale and hate to buy simple things like that over the net. Well I just found a kit and grabbed it up when I saw it.

http://www.meijer.com/s/kokido-6-way-pool-water-test-kit/_/R-215999

Now since I've been using it, it shows that my chlorine levels are fine and my pH levels are around 7.5-6ish. But when I look at the strips, the pH looks closer to 7.2-7.4, chlorine 5, and free chlorine as 0.5-1. The above kit doesn't test free chlorine. Is this a stat I should worry about so long as the overall chlorine is doing fine?

[TdiDave]

Free chlorine is the main thing to watch. If you have 5 total chlorine and 0.5 free chlorine you may have some issues and need to shock.

[spidey9]

Test strips are worse than useless, as they can give you the impression that everything is okay when it is not.

Based on the recommendations in this forum, I invested in a Taylor K-2006 kit before my tub had even been delivered, and next to the tub itself, it is the most important piece of gear that I own. I use it on a daily basis, and cannot imagine maintaining my tub without it.

As TdiDave pointed out, it is important to get a kit using the FAS-DPD method of testing, which allows you to differentiate between free and combined chlorine. Total chlorine does not tell the whole story.

I do not understand your aversion to ordering a kit online. I ordered not only the kit, but most of my chemicals and accessories online. I get exactly what I want, I do not have to deal with uninformed sales people pushing a particular product line, and I save a ton of money in the process.

[waterbear]

The kit we generally recommend is the Taylor K-2006 (not the K-2005) It is a far cry from the test kit you linked to in your first post. Any liquid kit is generally better than strips BUT it does need to test the parameters needed and an inexpensive OTO based kit (such as the one you linked to) is not going to do the job.

[Rubicon01]

I am also looking for a kit for my new experience with owning a hot tub and dealing with water chemistry for the first time in my life. I remeber the days of owning a fish tank and dealing with those annoying color charts that I could never really feel 100% confortable about where my color was

Is there a Digital kit that will do the same as the Taylor kit 2006, so I dont have to mess with color charts and instead just read numbers \ values?

Also is there a kit that is recommended for the HotSprings Ace Salt System that I should use? I am not sure how many different things a kit should test for that I will need to know about, so I want to make sure I get a kit that will do all that I need.

Thanks in advance...

[chem geek]

The digital kits have their own problems, mostly with high CH levels. The one digital kit that is decent (until you get to very expensive professional systems) is the LaMotte ColorQ Pro 7 (other similar ColorQ kits are OK as well, but the Pro 7 has the same tests as the Taylor K-2006 except it's DPD based). Because the chlorine test in the ColorQ is DPD-based, it can bleach out at high chlorine levels above 10 ppm. It doesn't read CH levels above around 300 ppm accurately. For the HotSprings Ace Salt System, there is nothing special needed for that. They force the CH low, but you should still test it to confirm. The only other test you need for that system is a salt test where you can use either the AquaChek® White Salt Titrators test strips or the Taylor K-1766 -- I find the latter to be more accurate though high accuracy for salt is not required.

By the way, realize that the Taylor K-2006 is a test where for most items you COUNT THE DROPS, so it's not about comparing colors. The only test where you compare colors is the pH test. For the FAS-DPD Free Chlorine and Combined Chlorine tests, you count the drops until the sample goes from pink/red to clear. For the Total Alkalinity test, you count the drops until a color change from green to red. For the Calcium Hardness test you count the drops until the sample turns from purple to blue. The CYA test is a visual turbidimetric test where you stop adding drops when the black dot disappears and you read the level in the tube. Go to this link and click on Pool/Spa on the left-hand side and scroll down to the K-2006 videos for each test to see how easy they are to perform.

[Rubicon01]

Because the chlorine test in the ColorQ is DPD-based, it can bleach out at high chlorine levels above 10 ppm.

It doesn't read CH levels above around 300 ppm accurately.

First, thanks for the reply \ information.

Based on the first statement, isn't the ColorQ Pro 7 kit using the same DPD based test as the Taylor kit, so wouldnt both the Taylor kit and the ColorQ Pro 7 kit be in the same boat? - bleaching out at high Chlorine levels above 10 ppm?

Based on the second statement, this means the ColorQ Pro 7 isn't as good at reading CH levels above around 300 ppm accurately whereas the Taylor is?, is that correct?

Thanks again!!!

[chem geek]

They aren't the same because the Taylor kit uses FAS-DPD so while the DPD dye is the same, the way you measure is by back-titrating using FAS reagent so counting the drops until it goes from pink/red to clear. If you add DPD powder and get a flash of pink that goes clear, you simply add more powder. That let's one measure accurately up to 50 ppm FC, if needed, and with a resolution of 0.2 ppm, if needed. The actual color of the sample when you add the DPD powder doesn't matter and it doesn't even matter if it's bleached out since adding FAS will have it actually increase in intensity (unbleaching) before it starts dropping again towards getting clear.

See this PDF file for more info on the FAS-DPD test and see especially Figures 2.1 and 2.3 to understand why DPD and FAS-DPD are different.

With DPD, it's accurate with a good colorimeter until somewhere in the 5 to 10 ppm range, depending on the chlorine neutralizers that are used, but then the dye gets oxidized by excess chlorine and starts to get lighter. So one first has a linear relationship of color vs. chlorine level and then a non-linear relationship and then an inversion where it gets lighter. Very high chlorine levels bleach out the dye completely.

Yes, your understanding of the CH test is correct that the Taylor keeps measuring accurately at high CH levels while the ColorQ loses accuracy above 300 ppm, usually reading too low.

[Rubicon01]

They aren't the same because the Taylor kit uses FAS-DPD so while the DPD dye is the same, the way you measure is by back-titrating using FAS reagent so counting the drops until it goes from pink/red to clear. If you add DPD powder and get a flash of pink that goes clear, you simply add more powder. That let's one measure accurately up to 50 ppm FC, if needed, and with a resolution of 0.2 ppm, if needed. The actual color of the sample when you add the DPD powder doesn't matter and it doesn't even matter if it's bleached out since adding FAS will have it actually increase in intensity (unbleaching) before it starts dropping again towards getting clear.

See this PDF file for more info on the FAS-DPD test and see especially Figures 2.1 and 2.3 to understand why DPD and FAS-DPD are different.

With DPD, it's accurate with a good colorimeter until somewhere in the 5 to 10 ppm range, depending on the chlorine neutralizers that are used, but then the dye gets oxidized by excess chlorine and starts to get lighter. So one first has a linear relationship of color vs. chlorine level and then a non-linear relationship and then an inversion where it gets lighter. Very high chlorine levels bleach out the dye completely.

Yes, your understanding of the CH test is correct that the Taylor keeps measuring accurately at high CH levels while the ColorQ loses accuracy above 300 ppm, usually reading too low.

Once again thanks for the thorough reply!

Can you help me decide between Taylor and the TF100 (I believe its called)? From what I read on the TF100 site it seems they bottle their own kit with same chemicals as Taylor with a larger quantity of drops for ultimately more tests per type of test. Plus they seem to have an edge in freshness / shelf life since they know how long their stuff will last based on when THEY bottled it. I believe they both are almost the same number of tests.... right? Can you help sway me one way or the other?

Thanks....

[waterbear]

Get the Taylor. The lack of acid/base demand tests in the TF100 is a minus as is the lower resolution pH test. FWIW, I wrote the original comparison of the two kits on TroubleFreePools for Dave when he first started his TFtestkits business (and was one of the kit's 'beta testers" ) and I slanted that comparison a bit to help him get his business off the ground but the pH test in the Taylor kit and the acid and base demand tests are the way to go. If you really want an OTO test then add a Taylor K-1000 kit (about $10) to the K-2006 and you have everything in the TF100 and more (including the pH test included in the TF100 AND the high precision pH test with acid and base demand included in in the K-2006)! As far as the freshness, they are buying from Taylor in bulk so their is no guarantee that their reagents are any fresher. Taylor can track a reagent by the number on the original bottle but you can't do that on a repackaged one. REagents do have a shelf life so you really do not want to have TOO much on hand but if you want larger bottles you can always order a K-2006C which has 2 oz bottles instead of 3/4 oz bottles.

Also the CYA mxiing bottle included in the Taylor kit is a bit better (IMHO) than the one included in the TF100, which has a stuck on label for the markings so it can be less precise in measurement (Dave once told me he had his family sticking on the labels, Don't know if he still does or not.)

Based on the second statement, this means the ColorQ Pro 7 isn't as good at reading CH levels above around 300 ppm accurately whereas the Taylor is?, is that correct?

Thanks again!!!

The Taylor is a titratrion (drop counting) test while the colorQ CH test is colormetric (color matching using a meter), Tritrations do not have the limitations that colormetric tests do.

[Rubicon01]

Get the Taylor. The lack of acid/base demand tests in the TF100 is a minus as is the lower resolution pH test. FWIW, I wrote the original comparison of the two kits on TroubleFreePools for Dave when he first started his TFtestkits business (and was one of the kit's 'beta testers" ) and I slanted that comparison a bit to help him get his business off the ground but the pH test in the Taylor kit and the acid and base demand tests are the way to go. If you really want an OTO test then add a Taylor K-1000 kit (about $10) to the K-2006 and you have everything in the TF100 and more (including the pH test included in the TF100 AND the high precision pH test with acid and base demand included in in the K-2006)! As far as the freshness, they are buying from Taylor in bulk so their is no guarantee that their reagents are any fresher. Taylor can track a reagent by the number on the original bottle but you can't do that on a repackaged one. REagents do have a shelf life so you really do not want to have TOO much on hand but if you want larger bottles you can always order a K-2006C which has 2 oz bottles instead of 3/4 oz bottles.

Also the CYA mxiing bottle included in the Taylor kit is a bit better (IMHO) than the one included in the TF100, which has a stuck on label for the markings so it can be less precise in measurement (Dave once told me he had his family sticking on the labels, Don't know if he still does or not.)

Does the average spa owner or one with the Ace Salt System need to do the OTO test? Not sure exactly what the OTO test is. I think I read on one of the forums that its a TOTAL chlorine test. If that is right, then isnt the Taylor Kit measuring both free and combined chlorine which would = the total chlorine. Sorry newbie here.

Thanks!

[chem geek]

The OTO test is useful as a quick test to see roughly if there is chlorine and it won't bleach out and yes it tests for Total Chlorine, but you are right that for accuracy one wants to use a FAS-DPD chlorine test where you "count the drops" until the sample goes from pink/red to clear. The FAS-DPD also distinguishes between Free Chlorine and Combined Chlorine. The DPD test does as well but it can bleach out and not be accurate at higher chlorine levels.