I notice the 9056 DPD comparator goes to 10 after many years of being limited to 5. Taylor made a big deal in their blurbs for the new extended range comparator about how great it is. So I was wondering if there is any technical reason why Taylor couldn't do the same for the OTO comparator. Searching the forums and indeed the whole Internet I couldn't find any technical reason for the current limit so I'm thinking it is just market driven.
Any technical reason OTO chlorine test limited to 5 versus 10 ppm?
- Thread starter Poolzzz
- Start date
The shades of yellow are already very hard to distinguish adding more shades would be doubtful to help 
There is a "loose" scale posted around here somewhere. Where the shade starts to get deep yellow, then orange, then deep orange, etc
There is a "loose" scale posted around here somewhere. Where the shade starts to get deep yellow, then orange, then deep orange, etc
- May 23, 2015
- 24,381
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
Just order the 9056 comparator and the R-0001/R-0002 reagents. Or purchase a K-1001 kit or K-1004 and add a 9056 comparator to it. Much more accurate than OTO and you can actually titrate the resulting pink solution to a clear endpoint using the R-0871 drops just as if you used the powder (R-0870). The precision is roughly 0.5ppm/drop.
OTO is simply inaccurate above 5ppm. It is not a quantitative test and should never be used that way.
OTO is simply inaccurate above 5ppm. It is not a quantitative test and should never be used that way.
There's no comparator to read above 5 ppm! I wouldn't expect accuracy without a proper comparator.
Maybe there's a technical limitation in the chemistry but if there is I haven't seen that described anywhere. Hence the question on the table.
- May 23, 2015
- 24,381
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
See Page 8 - https://www.hach.com/cms-portals/hach_com/cms/documents/pdf/LIT/L7019-ChlorineAnalysis.pdf
The method is simply inaccurate and has low specificity (i.e., color distinctions) and so making a comparator up to 10ppm would be pointless because the value is meaningless. OTO is simply not QUANTITATIVE - even at lower chlorine levels you can't say that a 5ppm yellow color is actually 5ppm. This is the very reason why I stopped using OTO all together. I could have total chlorine levels anywhere from 2 to 8ppm (as measured by FAS-DPD) and the yellow color was always the same shade. It's really a useless test.
The method is simply inaccurate and has low specificity (i.e., color distinctions) and so making a comparator up to 10ppm would be pointless because the value is meaningless. OTO is simply not QUANTITATIVE - even at lower chlorine levels you can't say that a 5ppm yellow color is actually 5ppm. This is the very reason why I stopped using OTO all together. I could have total chlorine levels anywhere from 2 to 8ppm (as measured by FAS-DPD) and the yellow color was always the same shade. It's really a useless test.
I asked Taylor why they stop at 5ppm. They said current industry recommendations for FC in residential pools is 2-4 ppm with a max of 5ppm. So as i suspected they are just following the market. Nothing more complicated than that.
Hmm, that's an interesting response considering that Taylor also makes the reagents for the FAS / DPD test that can very accurately measure FC up to 50ppm. While that test is aimed at commercial pool services, there is nothing that states it is not to be used commercially in a residential pool.
I think that whoever you spoke to simply told you what they believed you wanted to hear......
Yes, they said that too. The commercial market is driven by public health standards which currently has a maximum of 10 ppm. It's all based on the standards of intended market.