Taylor chlorine comparator

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Funny, my comparisons between the DPD-only and FAS-DPD are always spot-on.

What water sample size did you use for the FAS-DPD test - 25mL or 10mL?

Also, you could try diluting you test sample 1:1 with distilled water in the DPD only test (dilution marks are on the side of the tube) and see if your color changes proportionally.
 
I used the 10ml for the FAS-DPD. And then drops X .5 to get the result. That is what the large index card says that came with it. I didn't know you can do 25ml too.

As far as the 1:1 method with the DPD. I never tried it, but it was my understanding to only use that method to obtain results higher than the comparator reads.

Edit: I just re-read the 25ml test under "Notes" on the FAS-DPD Test page in Pool School. I'm prone to think I am doing something wrong with the plain DPD. Although not really sure what that can be as it's been what I have used for years before I got the FAS-DPD test. Wondering now if I have always run a higher CL level than I thought I was in the past.
 
25mL and two scoops of powder yields a finer titration - 0.2ppm/drop

You can use dilution whenever you want. I was thinking that if your at 3ppm then diluting it would drop you to 1.5ppm which would be a much lighter shade of pink. You could even use a diluted sample with the titration test to see if the drop count is halved. Just a way of verifying your results.
 
Thanks JoyfullNoise. I was actually editing my post above that I was reading up on the 25ml test probably at the same time you replied.

I am going to experiment with all these other methods tonight. If conditions are right I will get some photos too. Maybe the answer is I am completely color blind to shades of pink.
 
mikemass said:
Maybe the answer is I am completely color blind to shades of pink.
Click to expand...

Ask someone else to look at the color and give you their opinion. It helps to get confirmation.

I typically like to use bright, high sun (early afternoon) whenever possible as it creates the least amount of color distortion. Late afternoon or setting sun can add red components (at least where I am, we get fiery red and orange sunsets) to the light. Your white siding is a good choice though.

I've never seen more than a 0.5 to 1ppm difference between the two tests and I can typically get pretty close to a perfect match most times. So I'm a bit perplexed by what you're seeing. Obviously the titration results are the most accurate and should dose based on those tests.
 
Mike,

I measured my pool water today using my K-2006 titrating reagents AND my R-0001/R-0002 DPD only test kit. Here are my results -

K-2006 : All titrating samples are 25mL volumes

FC = 5.0 ppm (a little high because I have a pool party coming up tomorrow)
CC = 0.2 ppm
TA = 60ppm
pH = 7.6
CYA = 80ppm

(CH = 850ppm from beginning of season...I don't measure this frequently)

Here's what the high range #9056 comparator looks like (5 drops each of R-0001/R-0002 and R-0004 for pH) :

108EED8D-78F7-47EB-92CA-658CC7E4462D_zpshlgsd1ml.jpg


I tried my best to get into onto a bright white background (my new chase loungers that my wife got me for Father's Day). Unfortunately, no matter how I angled the cell phone camera, I would get some reflection off the front of the comparator. I walked around to several different spots in my yard and they all matched 5ppm. So, by my eyeballs, I call that pink shade equal to 5ppm FC and the pH is 7.6.

As you can see, my DPD-only test is dead-on with the FAS-DPD.

Hope this helps,

Matt
 
JoyfullNoise - That's a great pic you took. Yes I clearly see a 5ppm on the comparator as well. I tried again last night and came out with 2.5 DPD (maybe closer to 3 - My wife thought 3) and 5.5 FAS/DPD. I am clearly doing something wrong. I tried to video it to see if you can determine where I am going wrong but the video came out terrible, kids kept interrupting me. Making fun of me videoing my experiment. So I am too embarrassed to post it with their antics going on in the background. I will get another and follow up.

What bizarre is that the DPD always seems to be exactly half the FAS/DPD which indicates to me that I am dosing wrong. Even though I am fairly confident it's the DPD that is the wrong reading, I bumped up the SWG a little bit today for piece of mind. I'll report back tomorrow if I can get a good video tonight. (when I say tonight - 6:00pm usually which is still plenty of natural daylight)
 
jblizzle said:
What size of water sample are you using for the FAS-DPD and what multiplier are you using?
Click to expand...
10ml
Drops X 0.5 = FC

When I do it later I am going to try the 25ml and 0.2 method. I was staying away from this because of this statement in Pool School:

There isn't normally any reason to do this, but if you need more precision you can do this test with a 25 ml sample of pool water and multiply the number of drops by 0.2. In most situations the added precision is useless and simply wastes reagent.
Click to expand...

But maybe in my case it's worth going for the extra accuracy.
 

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So this is unusual because it would be easier to explain if the DPD only test was registering higher which is typically what people experience.

So FAS-DPD is 5.5ppm and DPD is 3. If you assumed the FAS-DPD test was wrong (reading too high) then the only thing that could produce a result that is too high is if the titrating droplets are 50% smaller than normal. That's not usually the case as most people tend to squeeze too hard, not too soft.

If you assume the DPD only test is wrong (too low), then the cause of that would be too little of the R-0002 reagent (color intensity is proportional to proper amount of DPD available to react with chlorine). That could happen if your drops are too small OR the reagent itself is compromised (which can happen with age).

How old is your bottle of R-0002?
 
mikemass said:
About a year. 15 months tops as I bought kit early in the season last year. Regardless, I just placed an order for the refill of both R-0001 & 2 for piece of mind. They will be here Saturday.
Click to expand...

Ok.

The R-0002 solution (brown dropper bottle) should be clear. A compromised R-0002 reagent will look cloudy greyish-purple but it can go bad without a good visual indication too so it can be hard to spot.
 
Big thanks to JoyfulNoise and jblizzle for continuing to bear with me and respond to my questions. Video is 8 minutes long, so if you have the patience to take a look and see if you see anywhere I am going wrong I appreciate it.

I choose to go with the 25ml/.20 factor on the FAS-DPD this time. But same results: 3ppm on the Taylor #9056 comparator vs 5.4ppm on the FAS-DPD titration. I held the block up to different backgrounds, so when you get to those points in the video, perhaps pausing and taking a look will help. If you think I am completely nuts and color blind, that is fine too. I am looking for any answers. My new R-0001 & 2 reagents are arriving this Saturday. I am hoping the age of the reagents is the answer.

I suggest watching in full screen mode (by clicking on the youtube icon - lower right) on a desktop for the best clarity. Thanks again.

 
I wish I had an answer for the discrepancy; hopefully the new reagent will fix it or someone will identify the problem. I've been thinking of getting that kit for daily testing by the pool because the pH has a tighter range than the one that came with the TF-100, and the chlorine goes to 10ppm. But I'll wait to see how your difference is resolved :)

I do have a tip for handling the R-871: I too find that it wants to dribble out when you first tip it over. What I do is squeeze the bottle a little bit while it's still upright, then release as I'm turning it upside down. That bit of negative pressure keeps any drops from coming out until I positively squeeze it again to get one at a time.
 
jmastron - Excellent suggestion with the R-0871 bottle. I have actually tried this as well. My issue (if you can call it that) is with that method you have to gently "release" your grip to get the drops coming out. Release too quickly and the drop falls too fast. I have much more control when I am applying a slight "squeeze" on the bottle and let the drop "fall" off the tip. I know I am wasting 3 -4 drops of reagent doing it that way, but it gives me a better feel of the drops. It's all about one's fine motor skills. (which I apparently lack with the "release" of my squeeze.) LOL

I am hoping as I use more and more reagent and the bottle empties a bit it won't rush out when I turn it upright.
 
mikemass said:
jmastron - Excellent suggestion with the R-0871 bottle. I have actually tried this as well. My issue (if you can call it that) is with that method you have to gently "release" your grip to get the drops coming out. Release too quickly and the drop falls too fast. I have much more control when I am applying a slight "squeeze" on the bottle and let the drop "fall" off the tip. I know I am wasting 3 -4 drops of reagent doing it that way, but it gives me a better feel of the drops. It's all about one's fine motor skills. (which I apparently lack with the "release" of my squeeze.) LOL

I am hoping as I use more and more reagent and the bottle empties a bit it won't rush out when I turn it upright.
Click to expand...

It gets better, but 4-5 drops always seems to want to come out on their own. I may not be describing it right -- I still squeeze to get the drops to come out (gently so they "fall"); all I do is squeeze a bit of air out while the tip is facing up, then release that (slight) squeeze as I rotate the bottle upside down. After that it's the same squeezing to coax each drop out. I could make a video, but it won't be as cool as yours :)

I do hope we get to the bottom of your measurement discrepancy.
 
mikemass said:
Big thanks to JoyfulNoise and jblizzle for continuing to bear with me and respond to my questions. Video is 8 minutes long, so if you have the patience to take a look and see if you see anywhere I am going wrong I appreciate it.

I choose to go with the 25ml/.20 factor on the FAS-DPD this time. But same results: 3ppm on the Taylor #9056 comparator vs 5.4ppm on the FAS-DPD titration. I held the block up to different backgrounds, so when you get to those points in the video, perhaps pausing and taking a look will help. If you think I am completely nuts and color blind, that is fine too. I am looking for any answers. My new R-0001 & 2 reagents are arriving this Saturday. I am hoping the age of the reagents is the answer.

I suggest watching in full screen mode (by clicking on the youtube icon - lower right) on a desktop for the best clarity. Thanks again.

Click to expand...

Mike,

Agree with your procedure and results; something squirrelly going on. When you held the comparator up to your white siding, it definitely looked like 3ppm (maybe a slight bit darker) for the DPD only test. Personally I thought the drops coming out of your FAS titrating reagent bottle looked to be on the small side to me but not 50% smaller. I would caution you to be careful with letting the reagent drop out and creating a vacuum inside the bottle - intentionally causing an internal vacuum can affect the droplet sizes. I have never used a TF-100 titrating reagent bottle but they are a lot different than the standard Taylor 2oz bottles. When I turn my Taylor bottles over, they never drip except maybe when they are first opened and filled up all the way. The Taylor bottles I have always used can be inverted without reagent self-dispensing. The only Taylor reagent bottle that has ever self-dispensed on me is the large, 2oz R-0009 for TA measurements and that is just due to the nature of sulfuric acid solutions being more dense than water.

That said, I just measured my pool water. I had a pool party yesterday for my oldest sons 11th birthday and he had 10 of his friends over. They swam for hours and the pool was a slight bit cloudier by the end of the day. I had pre-dosed my pool with 10% LC prior to the party raising my FC up to ~6ppm. After the party was over, I used the rest of LC in the gallon bottle I had. The pool water by this morning was back to it's usual crystal clear state. I decided to test my pool water with both titration and the standard DPD only test. Here are my results -

(I used the 10mL sample size for titration because I knew it would be high, so the sensitivity is 0.5ppm/drop) -

FC = 9.5ppm
CC <0.5ppm (barely a hint of pink that immediately cleared with one drop)
TA = 70ppm
pH =7.6

Because 9.5 is the top of the range for the DPD only comparator, I did a 1:1 dilution of the sample with distilled water (4.5mL DH2O and 4.5mL pool water). This is the result -

417F9015-4E22-45E1-8A41-A7FDAC7E4767_zpsvli0pycl.jpg


As you can see, the comparator color is darker than the 3ppm mark but lighter than the 5ppm. I say its closer to 5ppm than 3ppm and I would normally call that 4ppm to 4.5ppm (so 8-9ppm with dilution). Given that sample dilution technically makes the tolerance of test worse (in that range the tolerance is +/-1ppm so dilution should make that worse), my DPD-only results match my titration results fairly well.

Let's see what your new reagents do for you when they arrive. Hopefully it's just a matter of the R-0002 you have being a little old.

Matt
 
Hey Matt. Sorry I didn't respond sooner. I did receive my new R-0001 & R-0002 on Saturday and tested. Just haven't had time to post results till now.

Well, it appears my older reagents did indeed exceed their life expectancy because I did get a higher result with the new reagents. I didn't take photos, but with the new reagents I was getting a color match to 5ppm. Then I rinsed out the test block and used the "old" reagents. I was getting a reading somewhere between 2 & 3 ppm (similar to what the video from the other day showed. I didn't bother trying another FAS-DPD test because the comparison between the old and new reagents was conclusive enough.

I am starting to doubt myself if I did buy those reagents last year. Maybe they were older. Regardless I tossed them in the garbage and this time I marked "6/16" on the new vials. (FYI - new vials which came directly from Taylor has an expiration date stamped on it. My old ones, which was also genuine Taylor did not - only a lot number).

Moral of the story: Throw Out Your Old Reagents. They DO Go Bad.

Now to figure out why my R-0871 bottle dispenses 3 -5 drops on it's own when I invert it. Perhaps for my next test, I will get a bottle directly from Taylor and see if there's a difference. But that will be for another day (and thread).

Again - Thanks to everyone who took the time to read through this and offer suggestions.
 

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