Why are test strips so inaccurate?

[archjeb]

Although I have and use the Taylor FAS-DPD & complete service kit....sometimes I like to do a quick test or send the kids out to get a ball-park test with the test strips. But I still don't understand why the results are so different than the test strips?

The Free Chlorine & TA seems to be close / ok. But the Cynauric acid is WAY off. I'm talking significantly. Test strip shows below 20...but yet when I test with the Taylor kit...I'm at 80.
Total Chlorine seems to be off. pH, close, but still not accurate. Current Taylor tests show a pH of 7.5 but test strips show more alkaline.

Here is the test strips. Is it this brand? Or are they all not worth using? I love the Taylor test kit...but sometimes its nice to send the kids out to do a quick test to see where things are at. But at this point, I'm only using them for FC...since I can't trust them for anything else.

 

[archjeb]

oops, I did a search and found a similar recent thread on this subject.

Most recommended test strips?

I'm currently using the FAS-DPD test kit to get my water in balance - my plan is to have it to where I can use quality test strips once a day to show me that I'm good enough or that something might be off, and only have to use the Taylor kit once or twice a week to get a detailed reading of...

www.troublefreepool.com

I guess from that thread...they all suck, thus called guess-strips.

Wonder why they can't have a more accurate strip made?

 

[Texas Splash]

Consider these 3 areas:
Ranges & Limitations: Do you want accuracy of a bullet or to just "in the area" like a hand grenade? Sounds silly but it's true. Do you want an FC of 6 or an FC "somewhere" between 5-10? Makes a big difference. In addition, what if you are doing a SLAM Process and require an FC of 20? Can't do it on strips. Remember they list what "they" believe to be acceptable ranges. If you're not in one of those ideal areas you are not right.

Paper/Chemical Accuracy: How can we ever believe that both the chemical composition of each colored block and/or the paper they are adhered to are accurate and reliable?

Human/Visual Perception: It can be difficult to confirm a chemical reading to any degree of accuracy based on those shades. It's simply too difficult.

The reagent drop testing of the TF-100 or Taylor K-2006C test kits surpass in all of those areas with precision and reliability.

 

[mknauss]

In addition to Pat's comments, if they could make a better one they would. It just is not possible.

But --
Most pool owners think that cloudy water, some algae, red itchy eyes, and the occasional ear infection is normal. Honestly. So for that quality, the strips are just fine.

 

[Donldson]

Wonder why they can't have a more accurate strip made?

They can. Two caveats though.

First, you'd have to be willing to pay a bit more. The strips you show cost about 14 cents per strip. The ones that are more accurate go for something along the lines of $5 a strip. No, I'm not joking, Taylor Technologies makes them and you won't find them at pool stores (either on the shelves or behind the counter).

But realistically if you're paying that much for something accurate you're not going to be comparing it to colors on the back of a bottle. You need a very precise and accurate photometer to read them. They run for about $2500.

And that's the rub, you can get strips that rival or maybe surpass the accuracy of the tests in the TF-100/k-2006 but it will cost you thousands more for the privilege.

A bottle of test strips are a cheap consumable item with minimal QC effort to maintain accuracy and absolutely bottom of the barrel precision. If you can find it on a pool store or Walmart shelf then it's junk.

 

[archjeb]

I like the grenade analogy...

My son is getting old enough that I'm starting to teach him out to use the Taylor K-2006C reagent test kit - so easier tests are not as necessary as before. But, it would be nice to have an easy test strip method when I'm out of town and we have someone (like sister in-law) house-sitting...but I guess that is a utopian world that does not exist

 

[mknauss]

The OTO is OK for those days someone needs a basic kit. You can train your eyes on what color yellow matches your pools FC.

Your kit does not have the OTO -- but you can get a K1000 kit (the TF kits have them) for a few bucks.