TF100 DPD FC Results always higher than Taylor 9056 Comparator - why?

[JMPool99]

I use my TF100 regularly to check my Chlorine. I use the DPD powder test for FC. I used my Taylor 9056 comparator cylinder (from a Taylor 2000 series kit I had) and the FC results are always LOWER.

So, for the last month, I have been tracking the reading -- below are a couple samples.

TF100 DPD = 8.0 FC // Taylor 9056 Comparator cycline = 5 FC
TF100 DPD = 5.5 FC // Taylor 9056 Comparator cylinder = 3 FC

Why would my DPD Powder test always return such higher results? I've been using the DPD Power for months and I'm sure I'm doing it correctly -- my readings are always consistent with the DPD Powder (I've done them back to back before).

Would love some insight as to why the DPD Powder results are always higher than with my test with Taylor 9056 Comparator.

Thanks!

 

[ajw22]

The FAS/DPD is the most accurate FC test which is why we recommend it.

The DPD test is more accurate then your calibrated eyeball.

 

[JMPool99]

I get your point on the colors and visual, but the 9056 is larger and gradients are easier to align. The fact that it's consistentl 2.0-3.0 under what the power DPD results are really has me wondering is all. In all fairness, I'm sure if I called Taylor they would tell me their 9056 Comparator is more accurate... right?

Are there any other brand DPD Poweder test out there? If so, I might purchase so I can compare those results to the TF-100 DPD powder results.

 

[duraleigh]

I'm sure if I called Taylor they would tell me their 9056 Comparator is more accurate... right?

I doubt it. The R-0870 and R-0871 found in the TF-100 FAS/DPD test are, in fact, Taylor Products - always have been. The test you are comparing it to is an OTO test not known for accuracy but known for dependability. Taylor techs should tell you exactly the same thing.

 

[ajw22]

I get your point on the colors and visual, but the 9056 is larger and gradients are easier to align. The fact that it's consistentl 2.0-3.0 under what the power DPD results are really has me wondering is all. In all fairness, I'm sure if I called Taylor they would tell me their 9056 Comparator is more accurate... right?

Wrong. The TF100 uses Taylor reagents and is identical to the Taylor FAS/DPD test.

Taylor will tell you the FAS/DPD test is a more accurate test then the comparator block.

Are there any other brand DPD Poweder test out there? If so, I might purchase so I can compare those results to the TF-100 DPD powder results.

TF100 uses Taylor reagents.

Using the Taylor standard gives us a standard baseline to give chemistry recommendations.

Other manufactures tests are known to give different results.

Pool Test Kits - Further Reading

www.troublefreepool.com

 

[Oly]

I too have observed this difference between test methods. I use the 9056 while in my spa to test FC. I would not use the FAS-DPD test in that situation but was aware of the consistent spread and dosed accordingly.

 

[JMPool99]

I too have observed this difference between test methods. I use the 9056 while in my spa to test FC. I would not use the FAS-DPD test in that situation but was aware of the consistent spread and dosed accordingly.

Ah -- glad to see someone else has experienced the same thing with 9056 vs. Taylor DPD powder test. That's crazy the results are different and always so consistently different! Wow.

And thanks everyone else for the replies. I fully intend to continue with my DPD poweder test, but understanding the difference was important to me.

 

[JMPool99]

Just for kicks... I did open a support case with Taylor -- figured heck why not! I'll report back here what they say if it's something worth sharing. Cheers!

 

[duraleigh]

From this point, refer to the powder test as FAS/DPD. In fact there is a DPD chlorine test that is in the Taylor K-2005 but it is quite a different test so don't confuse them

 

[JMPool99]

Spoke to Taylor -- they called me right back and were very helpful. As everyone here already said, they stated very clearly (the lady even escalated to confirm with a Sr. Tech) that the FAS/DPD is superior for accuracy. Taylor said HOAs, Health Agencies, etc. USUALLY all reqire the FAS/DPD test -- so that says something! Taylor would expect the results could be different by 0.5 - 1.0 ppm but the fact that I'm seeing 2.0 - 3.0PPM difference consistently has them curious.

In short... stick with the FAS/DPD and just accept that other results are inferior! That's my takeaway. THANK YOU ALL!

PS - Taylor did recommend their video archive for the K2006 (some solid videos).

K-2006 Complete™ Kit with FAS-DPD

LAST THING... I am going to buy a Taylor K-1515-A and follow their test instructions just to confirm consistent with my TF-100 results. Note: Taylor instructions do advise using 25ML and .2 as the multiplier.

 

[JoyfulNoise]

I use the 9056 comparator a lot for quick testing. It’s always lower as well. If my FAS/DPD test says 9ppm, the comparator reads closer to the 7.5ppm. But here’s a trick - the R-0871 titrating drops can be used to titrate the R-0001/R-0002 drops used for the 9056 comparator. I would suggest adding a 6th drop to the test sample. The multiplier will roughly be 0.5ppm/drop. See how many drops it takes to get the sample clear. I bet you’ll find that of you titrate the 9056 comparator sample it will be fairly close to your FAS/DPD test.

It’s all the same DPD chemistry. It’s just the drops and the powder are different ways of achieving the same result.

 

[duraleigh]

LAST THING... I am going to buy a Taylor K-1515-A and follow their test instructions just to confirm consistent with my TF-100 results. Note: Taylor instructions do advise using 25ML and .2 as the multiplier.

That entirely up to you. I am obligated to tell you again it is the SAME TEST, .2 resolution and a 25ml sample can be used on the TF-100 as well if you like but there is NO practical reason. That's your call as well.

 

[JMPool99]

That entirely up to you. I am obligated to tell you again it is the SAME TEST, .2 resolution and a 25ml sample can be used on the TF-100 as well if you like but there is NO practical reason. That's your call as well.

Noted! I was running low on powder anyway, so I can use this and then do a full TF-100 kit refill in a few months. THANKS!

 

[dfwnoob]

I bought Taylor-branded FAS-DPD test reagents off Amazon because I was running out quicker than I realized and I was in a crunch. They're 100% the exact same thing. Same powder, same liquid, same test results.

The chlorine side of my comparator never gets used.

 

[Newdude]

So @JMPool99. We strive for accuracy here, being the foundation that the house is built upon, but in this instance I will break from the pack. I never give a rats patootie about the number after the decimal point. .5, .2, .9362.... I want to see the number *before* the decimal point. The 2 FC is the massive problem. The 2.5 or 2.8 doesn't help the problem at all. Save your test supplies and use 10ml / .5 FC per drop. Just because you can test more percise, doesn't mean you should.