FC Testing: Taylor k2006 vs DPD 1 Photometer and Rapid tests

Jump to latest Follow Reply
S

SteveSwims

Well-known member
Jul 5, 2024
119
United Kingdom
Hi all

I have a Taylor K2006 test kit which gives me readings of around 4ppm FC (which line sup with what I’m expecting after adding chlorine etc…)

However, out of curiosity does anyone have any explanation as to why other DPD 1 tablet based tests (both rapid colour chamber comparison and photometer based tests) would only ever give readings of less than 1ppm using the same sample?

I’m fairly certain I’m using all test kits correctly so just curious what might cause both DPD 1 tests to be similar to each other whilst both being so vastly different to the k2006 results?

FYI, the test kits I’m comparing are

Taylor K2006
Water ID Pool Lab 2.0 (Water Tester 2.0 in the US) (Photometer)
Water ID Pool tester (rapid)
 
Last edited:
SteveSwims said:
Hi all

I have a Taylor K2006 test kit which gives me readings of around 4ppm FC (which line sup with what I’m expecting after adding chlorine etc…)

However, out of curiosity does anyone have any explanation as to why other DPD 1 tablet based tests (both rapid colour chamber comparison and photometer based tests) would only ever give readings of less than 1ppm using the same sample?

I’m fairly certain I’m using all test kits correctly so just curious what might cause both DPD 1 tests to be similar to each other whilst both being so vastly different to the k2006 results?

FYI, the test kits I’m comparing are

Taylor K2006
Water ID Pool Lab 2.0 (Water Tester 2.0 in the US) (Photometer)
Water ID Pool tester (rapid)
Click to expand...
Someone else will have to comment on the why, but the photometers are known to be unreliable and I was under the impression the DPD didnt read above 5ppm along with test tolerances being quite large.
 
Thanks, I had wondered about tolerance but it just seems that these readings would fall outside of any tolerance variations and (according to my Taylor kit) my FC rides between 3 and 4 ppm most of the time so shouldn’t be the cause of bleaching out the test I guess.

Just seemed odd that the DPD 1 based tests would read the same and both would be so drastically different to the Taylor results.

To avoid any doubt, my main testing (and my pool math results) are from the Taylor kit.

Just have the other tests and was was curious about the odd outcomes.
 
Digital photometers are known to go bad over time. They are critically dependent on having a stable light source (all light sources will age and change over time) and for the test tubes, cuvettes, to be clean and free from imperfection. Plastic cuvettes are horrible as they age quite rapidly just from heat and use. Glass cuvettes are better but still can become quite dirty. In my lab days, all photometers were constantly calibrated and standardized prior to use and reaction cuvettes (quarts glass) were single use, you threw them in the trash after the test was over. We NEVER used plastic cuvettes. Even with all the rigor of the lab environment, photometers would routinely need to be sent out for repair and recalibration and just as often needed to be replaced. That said, consumer grade photometers are toys in my opinion and I would never use them for residential pool care. The time saved versus drop based testing is minimal but the errors introduced are too great.
 
  • Like
Reactions: Newdude
The pool lab 2.0 does support user calibration but that obviously requires another method with which to test and verify it.

The test kit options available in the UK are basically test strips and photometers. FAS-DPD isn't legally available here so there are some real challenges to follow TFP methodology.

I do have a Taylor K2006 test kit but getting it is basically equivalent to getting hold of a load of Kinder Surprise Eggs in the US. Although I managed to get one I don't necessarily be able to get another once the reagents expire.

We frustratlingly have to work with what we can get.
 
  • Like
Reactions: Newdude
thanks for all the responses.

Just to clarify, my Pool Lab 2.0 photometer is brand new (bought primarily for the CYA testing range as my indoor pool only needs low CYA (below the range of the Taylor teat kit)

I was just curious about why DPD 1 based FC tests would yield very similar results to each other, whilst being vastly different to the Taylor k2006 FC results.
 
Newdude said:
We still recommend 30 CYA for bather comfort, instead of UV protection. Without CYA to buffer the HOCL, even a little FC is harsh. (y)
Click to expand...
I had him start with adding 20 and see where he was...I think he understands 20-30 is good...didn't want to overdo it with new pool...

Moved House - Now Have A Pool

Hi all First time pool owner in the U.K. here. Moved house in May this year and inherited what I believe is a roughly 10000 gallon in ground vinyl pool in the garden (within its own glass/brick building). Having never been a pool owner before I’m trying to learn fast (I’m reading pool school...
www.troublefreepool.com www.troublefreepool.com
 
  • Like
Reactions: Newdude
As I understand it they are actually restricted across the EU since 2019 (and the UK copied and pasted all those EU laws when it left). There are restrictions on high potassium component chemicals which fall under the classification of "explosives precursors" Regulation - 2019/1148 - EN - EUR-Lex

From what I've read the components of the FAS-DPD tests are too high in potassium components and no companies have gone through the very arduous task of getting approval. If they get approved every sale has to be monitored and reporting. I can see why none of the companies that previously operated here have bothered (Lovibond, Palintest, LaMotte)
 

Enjoying this content?

Support TFP with a donation.

Give Support
On the subject of things that are banned here, Muriatic Acid (more commonly called Hydrochloric acid) is massively restricted and requires a background check and government registration in order to buy a small quantity.
 
I don't really understand why @SteveSwims is getting such different results. I've currently got my pool at 4ppm FC and across my Taylor, PoolLab 1.0, PoolLab 2.0, Lovibond Pooltester Multipooltester 5 in 1 (DPD-1 rapid) I get very close readings - within 0.5ppm (but I did start with 10ml for the Taylor FAS-DPD test as my starting reference which was the odd one out at 0.5 higher).

I checked and my tablet reagents for all of the above are good until 2029, so about 7 years expected lifespan. The PoolLab 2.0 only came out last year so it seems very improbable the reagents would be expired.
 
Sorry to bump but just wondered if anyone else had any ideas as to why my DPD tablet based results (both photometer and colour comparison tests) would be so much lower than my FAS-DPD results?

The fact that the FAs-DPD seems to be the odd one out has me questioning it a little so just not sure!
 
The accuracy of photometric testing is not as accurate as the FAS-DPD/Taylor drop testing.

That accuracy for the photometric testing is with a calibrated machine and properly trained operator. Accuracy is worse if there is no calibration and the operator is not trained. Accuracy is worse when you have a unit that is calibrated at the factory and you have no way to recalibrate.

We have a similar unit in the US called ColorQ, it uses photometric test, crush pills etc. You can do a search here, many people, including myself have abandoned them.

We recommend the kits we do for this reason. We don't trust any other testing. The taylor tests work. I'm sorry you are in such a pisser of a situation. You have to make do with what you can...
 
  • Like
Reactions: Newdude
SteveSwims said:
@PoolStored

Thanks for the reply but not sure what the table is telling me? Are you able to clarify please?
Click to expand...
It means theres a 25% error tolerance on the chlorine test. If the actual FC level is 5ppm, they would consider results from 3.75ppm to 6.25ppm to be acceptable. Taylor drop test accuracy would be 4.5ppm to 5.5ppm.
 
Ah thanks, for clarifying.

For what it’s worth (and of course contains the “get out of jail free” card in the form of “under laboratory conditions…”), the Pool Lab 2.0 tolerance is +- 10% (screenshot from manual below).

The thing is I’m not just using photometer testing.

I’ve also got a DPD tablet based test (https://www.water-id.com/product/29/show)

My results from that test match the results from my Pool Lab 2.0 (ie usually around 0.5 / 1ppm FC).

However, 0.5-1ppm is drastically off from my Taylor k2006 FC results (around 4ppm).

I get that lack of accuracy comes into play here but a difference of at least 3ppm between the DPD tablet based tests (photometer and colour comparison) and the K2006 results are just throwing me a little.

If the photometer results and the DPD colour comparison test results were drastically different from each other then that would be a bit easier to accept that lack of accuracy was at play here.

But why would they both be so close to each other (every time) and why would that differ so greatly from the Taylor.

Just to re-iterate, my K2006 kit is my main test kit. It’s just curiosity (and a bit of uncertainty) making we wonder about these results (even if it’s a waste of time in the bigger picture 😂).
 

Attachments

  • IMG_8146.jpeg
    IMG_8146.jpeg
    99.3 KB · Views: 1
Last edited:

Enjoying this content?

Support TFP with a donation.

Give Support
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply