WaterGuru Sense Test v. TF-100

HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
I recently purchased the WaterGuru Sense after reading about it here. I liked the idea of not having to test the FC/PH everyday, so thought this might be a decent solution. As part of the program, you send them a vial of water for them to test at their lab...as I understand, this isn't the normal "pool store test", but an honest to God laboratory test that should be pretty legit. So, here are the numbers that WaterGuru came up with compared with what I got with my TF-100 (same sample time).

Value // Lab test // TF-100

FC 3.67 // 9.0
CC .24 // 0.5
PH 7.9 // 8.2
TA 80 // 70
CH 274 // 300
CYA 24 // 40

Phosphates 419
Salt 1488 (We do not have a SWG)
Copper 0.1
Iron 0.2

The only "surprise" is that of CYA. I thought I have been getting a pretty accurate # and during this test, I was getting it at the 40 or 50...certainly NOT 30. So, I am not sure what to think of that number. Also, I assume the FC is lower simply because it breaks down over the transit time to the lab.

I am also assuming that the iron and copper numbers are A-OK.

Still on the fence on the Guru. There is a 45 day trial period and the verdict is still out whether it's worth the $.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,959
Tucson, AZ
The WG and your TF-100 should be pretty close on FC/pH on a daily basis. However, at 9ppm FC, you're running pretty high for what the colorimeter can do inside the WG. Normally at 10ppm FC and above, you really want to do FAS titration to get an exact value.

The CYA number is difficult to nail down. All residential testers are going to be based on the occluded dot test which can be somewhat subjective. A proper test lab should be using an automated (digital) nephelometer which measures turbidity. When properly calibrated, a nephelometer can give +/-1ppm precision. The accuracy of the nephelometer will depend on how carefully it is calibrated. Normally, one uses a blank (zero) standard and a known standard to calibrate the output. The digital CYA tester from Hach can do all that, but it retails for around $500 and requires regular calibration. Without you testing the same solution side-by-side with the WaterGuru test lab, it's hard to say who is right. Erring on the high side with your TF-100 results is appropriate and will keep your water clean and clear. There is no danger of the FC being too high relative to the CYA values you've posted...you may be just using a bit more chlorine ...
 
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the_sphynx

Well-known member
Feb 19, 2019
68
North San Diego County
This is good stuff. I may have to pick up one these next year if we see the value here on the forums. I also like to run my chlorine a little higher than the recommended values for those "Just in case" things that might creep up. There absolutely comes a point where it's just wasted chlorine though so I try to keep it right about that 7-10ppm FC mark when possible.
 

HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
Do you have it tracking FC and PH daily and if so well is that working and how do its numbers compare to your manual testing?
It is tracking daily. There is no option to keep it from daily tests (absent removing the batteries) but the support folks said that the cartridges are good for only two months, anyway. It's been darn cold out and my FC has been pretty high, so I haven't been testing. I will get good numbers in the AM during my daily filter run.

The WG and your TF-100 should be pretty close on FC/pH on a daily basis. However, at 9ppm FC, you're running pretty high for what the colorimeter can do inside the WG. Normally at 10ppm FC and above, you really want to do FAS titration to get an exact value.

The CYA number is difficult to nail down. All residential testers are going to be based on the occluded dot test which can be somewhat subjective. A proper test lab should be using an automated (digital) nephelometer which measures turbidity. When properly calibrated, a nephelometer can give +/-1ppm precision. The accuracy of the nephelometer will depend on how carefully it is calibrated. Normally, one uses a blank (zero) standard and a known standard to calibrate the output. The digital CYA tester from Hach can do all that, but it retails for around $500 and requires regular calibration. Without you testing the same solution side-by-side with the WaterGuru test lab, it's hard to say who is right. Erring on the high side with your TF-100 results is appropriate and will keep your water clean and clear. There is no danger of the FC being too high relative to the CYA values you've posted...you may be just using a bit more chlorine ...
Thanks for all the good info! The FC being high is a bit leftover from a trip I took a while back. I bumped it up (and used pucks) for about 10 days and the FC has been *very* slow coming down. I am coming up on a year of owning the pool and maintaining *only* IAW TFP methods with nary and issue, so I think I will trust the TF-100 numbers. :)
 

kimkats

Mod Squad
LifeTime Supporter
Jul 10, 2012
45,528
Tallahassee, FL
The shipping of the water will "mess with" the pH values due to it being shaken and such in the trucks. If you take a bottle of water and shake it you can increase the pH so.........
 
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HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
The shipping of the water will "mess with" the pH values due to it being shaken and such in the trucks. If you take a bottle of water and shake it you can increase the pH so.........
Yep, and I actually expected the lab number to be higher. However, where folks seem to have issues with the CYA test, I have issues w/ PH. I can get 8.2 on one test and then 7.5 on the next (same water sample) and it seems to be with how *close* I get to the black line. It's really quite annoying and one of the reasons I went with the WG Sense.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,959
Tucson, AZ
Yep, and I actually expected the lab number to be higher. However, where folks seem to have issues with the CYA test, I have issues w/ PH. I can get 8.2 on one test and then 7.5 on the next (same water sample) and it seems to be with how *close* I get to the black line. It's really quite annoying and one of the reasons I went with the WG Sense.
That really should not be the case. Being off on the water sample volume by a small fractional amount should have no impact on the color difference. If you are truly seeing something like that, then there is something wrong with how you are doing the pH test or there is something contaminating your pH vial. I have used multiple Taylor pH comparators (both the #9056 and the midget comparator) and they are always spot on with each other. A small variation in sample volume has no affect on color.

Have you posted on this pH issue previously?
 

HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
That really should not be the case. Being off on the water sample volume by a small fractional amount should have no impact on the color difference. If you are truly seeing something like that, then there is something wrong with how you are doing the pH test or there is something contaminating your pH vial. I have used multiple Taylor pH comparators (both the #9056 and the midget comparator) and they are always spot on with each other. A small variation in sample volume has no affect on color.

Have you posted on this pH issue previously?
I have not. This is interesting as I have used two separate reagents and seem to have the same issue. I wouldn't think that contamination would be an issue since I rinse it thoroughly with the same water that I am sampling. Maybe I should get a light box...perhaps that might be my issue.
I never heard of the Water Guru before your post. Are you satisfied and feel comfortable with it’s test results? Is there much of a learning curve with this device or the app?
So far I am happy. There was a reporting issue with the temperature (online graph only showed 0-1 degree F) but was resolved by support folks pretty quick. There is another thread that discusses a longer period of time for testing, so that might be more useful.

Edit: Other user's experience: WaterGuru - A Test

I have been testing the FC/PH around the same time as the Guru is testing and they are pretty spot on. So yes, if you have a pool that has been easy to maintain (as in numbers don't need to be tested every other day) which really should be the case if you are using TFP methods, then I think it's worthwhile. At least it is for me, since I am not a huge fan of getting on my knees every day to get a water sample. It does have a 45 day trial period, so that should be plenty of time to determine if I *truly* like it or not.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
16,959
Tucson, AZ
I have not. This is interesting as I have used two separate reagents and seem to have the same issue. I wouldn't think that contamination would be an issue since I rinse it thoroughly with the same water that I am sampling. Maybe I should get a light box...perhaps that might be my issue.
I doubt you need a light box. Outdoor lighting with a white background (like a paper plate) should be more than sufficient. Minor variations in water sample volume will not make any difference to the color. Maybe you can purchase a Taylor K-1001 residential test kit on Amazon and check yourself against that. It comes with a midget comparator block and R-0014 phenol red (the phenol red concentration is different in the R-0014 to account for the smaller volume comparator block). Alternatively you can try to purchase a Taylor #9056 comparator and a bottle of R-0004 phenol red reagent. The larger comparator block gives you better graduations in pH. The pH reagent you have should be fairly stable but perhaps it got compromised in some way.
 
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HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
I doubt you need a light box. Outdoor lighting with a white background (like a paper plate) should be more than sufficient. Minor variations in water sample volume will not make any difference to the color. Maybe you can purchase a Taylor K-1001 residential test kit on Amazon and check yourself against that. It comes with a midget comparator block and R-0014 phenol red (the phenol red concentration is different in the R-0014 to account for the smaller volume comparator block). Alternatively you can try to purchase a Taylor #9056 comparator and a bottle of R-0004 phenol red reagent. The larger comparator block gives you better graduations in pH. The pH reagent you have should be fairly stable but perhaps it got compromised in some way.
Thanks for the info, I appreciate it. I ordered a Taylor 9058 but can't find documentation for which reagent to use.

Edit: Figured it out. It's the same as the 9056 but has CYA instead of the FC, so it uses the R-0004. Thanks again!
 
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HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
Just an update on the Waterguru. I have been using it now for about 6 months and still think it's worthwhile. I sent in another sample for a lab test since pool season is around the corner and here are the test numbers in comparison to TF-100. As you can see, the lab numbers line up pretty well with the TF-100.

Value // Lab test // TF-100

FC 4.12 // 7.5
CC .06 // 0.5
PH 7.8 // 8.0
TA 70 // 60
CH 291 // 275
CYA 53 // 60
CSI -0.04 // +0.01
Phosphates 458 (419 last test)
Salt 1403 (We do not have a SWG)
Copper 0.0
Iron 0.1
 

HeyEng

Silver Supporter
Nov 7, 2018
479
Oklahoma City, OK
What is the verdict? What additional costs are there? Is it just batteries, testing supplies, etc?
I have been happy with it. It uses "C" batteries (last a long time, they are still at 60%+ life left) and the cartridge lasts about 8 weeks (cost is $19.95 for one or $49.95 for 3).
 
I just ordered it. I have a 21' ag, so the skimmer is smaller than an ig pool (7"). I will have to fabricate some kind of adapter to make it fit. I have read good things about the guru so I am hopeful that it works. I will report back after it comes in.
 

amytude

Well-known member
Jan 14, 2013
68
I'm eager to try this, but also skeptical. I need it to just work within acceptable parameters so I don't have to be a chemist. My right-brained mind can hardly handle the TPF kit. Years later, I still have no idea how to do the CYA test.