Question about chlorine DPD powder

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spanoob9

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Jul 14, 2013
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I recently got a FAS-DPD chlorine test and the instructions say to add 2 dippers of powder. I know its better to add more than you need.

But I'm curious about,

Why 2 dippers? How much chlorine does 1 dipper of powder bond with? (Not sure I phrased that correctly..)

If I'm expecting a reading of less than 5 ppm can I use just one dipper?

And if I'm shocking to 20+ ppm is 2 dippers enough to test levels that high?

Also is the powder suppose to be 100% fine powder? Mine has a lot of crystals in it and they tend to sit at the bottom of the test tube not dissolving.

Thanks in advance
 
I have found and several others have stated they use one big scooping full of powder (well as big as that tiny scooping can be LOL). More is not always better. You are looking for the water to turn pink from the interaction. If it does so you are good. The times I pushed my FC to SLAM level I used the same amount of powder and it worked just fine.

I tend to shake up the container the powder is in because of the "crystals". I THINK the "crystals" are the same stuff the rest is only in a "rock" instead of "powder". I have not found any problem with one still being in there when I did the test. It just sat there.

Kim
 
Thanks for that from me as well, Kim. I found it makes no difference either, except that 2 scoops is brighter pink.

Is it OK to add a very closely related question? Should the scoop be cleaned off? It seems to be getting all black and ugly.
 
Has anyone found an effective way to crush the larger pebbles into finer dust? Those pebbles seem to jump around at the slightest movement of the scooper. Thought about pouring it all in a plastic baggie or Saran Wrap and crushing it up. Thoughts?
 
Funny how you always end up with pebbles in the dpd.

Wonder why they are not finely ground all the way.

spanoob are you not doing the 10 ml dpd test? with that you only need to use 1 scoop.

There are times that the 25ml 2 scoop test is warranted but shouldn't be needed most
of the time.
 
borjis said:
Funny how you always end up with pebbles in the dpd.

Wonder why they are not finely ground all the way.

spanoob are you not doing the 10 ml dpd test? with that you only need to use 1 scoop.

There are times that the 25ml 2 scoop test is warranted but shouldn't be needed most
of the time.
Click to expand...
Yes I am doing 10 ml test.

The directions don't say anything about use 1 dipper for 10, 2 for 25. Anyway it does turn pink after adding one dipper. Thanks for confirming!
 
Let me add a little missing information to this discussion.

First off, as someone who spent lots of time in a chemistry lab both using chemicals and developing chemical protocols, in my opinion, you should NOT mess with the directions that Taylor has set forth. If they say to use two dippers full of powder (ever so slightly rounded mound), then use two dippers full. There is a reason why they tell you to do this and it's not because there's some nefarious cabal of DPD powder manufacturers out there trying to get you to waste as much powder as possible so you can push up their corporate profits. It's more likely that Taylor did lots of testing of their reagents and found that two dippers works best.

Second, the powder is actually a combination of MANY different chemicals (I think there's something close to 5 or 7 distinct chemicals in the powder), of which the DPD is only a small fraction. The rest of the chemicals are there to adjust and buffer the pH of the water, sequester any interfering metals and stabilize the DPD against oxidation from anything but the chlorine in your sample. So, by using less than the prescribe amount, you could be inadvertently short-changing some of the other vital aspects of the chemistry.

Finally, unless you live outside the US, the powder is neither expensive nor hard to come by. It also has a shelf-life and is sensitive to moisture. So, trying to save a little bit of powder and extend the amount of time between buys probably makes very little sense when you consider that the reagent can be easily compromised and mess up your testing which is far more important than a couple of dollars worth of powder.

Just my opinion.....

Matt

PS - Don't crush up anything in a mortar & pestal. Not only is that totally unnecessary but your risk spillage and contamination of your reagent. The little crystals you see in the bottom of the vial will not affect the results of the test.
 

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Donldson said:
Taylor's instructions are for a 25ml water sample. As a 10ml water sample is only 40% of the water then I believe using 50% of the powder is more than enough to successfully perform the test.
Click to expand...

Agreed. I typically use a 25mL water sample.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
JoyfulNoise said:
..... Finally, unless you live outside the US, the powder is neither expensive nor hard to come by. It also has a shelf-life and is sensitive to moisture. So, trying to save a little bit of powder and extend the amount of time between buys probably makes very little sense when you consider that the reagent can be easily compromised and mess up your testing which is far more important than a couple of dollars worth of powder......
Click to expand...

I haven't tried this, yet, but another poster buys the FAS/DPD powder in 1/4 pound(113 g) packages ($26.00) and vacuum packs the container between refillings of the "everyday" vial. Obviously, an extra bit of hassle, but a savings of over $5, per vial.

That looks like about 2 seasons worth of testing powder [for me], so if I can keep it from going bad, economically, it works.
 
ewkearns said:
I haven't tried this, yet, but another poster buys the FAS/DPD powder in 1/4 pound(113 g) packages ($26.00) and vacuum packs the container between refillings of the "everyday" vial. Obviously, an extra bit of hassle, but a savings of over $5, per vial.

That looks like about 2 seasons worth of testing powder [for me], so if I can keep it from going bad, economically, it works.
Click to expand...

I have seen that as well. I simply do not use enough powder in a given season to justify getting such a large quantity. I suppose if you live in Australia or Canada, then buying a bulk quantity like that makes the most sense given the shipping difficulties and expenses involved. But for the average US pool owner, I can't see anyone using that much powder.

Once you get to know your pool water needs, daily testing with the FAS-DPD reagents becomes unnecessary. I use my "high precision" tests mostly at the beginning of the season to dial in my SWG and for a few spot checks throughout the season. On a daily basis, I simply use my K-1001 (DPD-only test) to make sure I'm in the range I need to be in. With the right comparator block and some simple dilution with distilled water, you can easily test all the way up to 10ppm FC. If things look "funny", then I fall back on my more accurate FAS-DPD test. This makes buying lots of powder each season unnecessary.
 
JoyfulNoise said:
I have seen that as well. I simply do not use enough powder in a given season to justify getting such a large quantity.

On a daily basis, I simply use my K-1001 (DPD-only test) to make sure I'm in the range I need to be in.
Click to expand...

I have a bit different approach. I'm as concerned with monitoring CC as I am FC, since I feel that gives me a heads-up for impending algae/etc. issues. Considering R-0870, R-0871, and R-0002 together, I have my chlorine test regimen down (using a 25 mL test sample) to less than 7¢ per test.... and I tend to test twice a day: Once in the AM, checking the overnight change and in the PM, after the sun goes down to see if Ol' Sol burned off too much chlorine...

If anybody is interested in the minutiae, the little blue spoon is a .05g measurement.
 
ewkearns said:
I have a bit different approach. I'm as concerned with monitoring CC as I am FC, since I feel that gives me a heads-up for impending algae/etc. issues. Considering R-0870, R-0871, and R-0002 together, I have my chlorine test regimen down (using a 25 mL test sample) to less than 7¢ per test.... and I tend to test twice a day: Once in the AM, checking the overnight change and in the PM, after the sun goes down to see if Ol' Sol burned off too much chlorine...

If anybody is interested in the minutiae, the little blue spoon is a .05g measurement.
Click to expand...

I can use the R-0003 reagent in conjunction with the R-0001 & R-0002 reagents in the K-1001 to test for CCs as well. I've gotten pretty good at seeing the color change.

Anyway, glad you've got it down to $0.07 per test. That's great!


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 
Everyone is different. ewkearns buying in large quantities makes sense because he tests 14 times each week. The majority of TFP members, after they get to know their pool, can test once weekly and manage pretty well. Large quantities of DPD powder to them could be a 10-15 years supply and that just doesn't work.

Everyone is different.
 
duraleigh said:
Everyone is different. ewkearns buying in large quantities makes sense because he tests 14 times each week. The majority of TFP members, after they get to know their pool, can test once weekly and manage pretty well.
Click to expand...

Indeed! And before I retired, there is no way I could have reliably tested 2 times per day. Besides the people that can't test that frequently, a lot of people just don't want to and they really don't have to, either. The beauty of TFP is that it is adaptable to every person that cares to learn and is able to take at least some part in their pool care.

Now, my pool, yard, and garden is my job....


duraleigh said:
Large quantities of DPD powder to them could be a 10-15 years supply and that just doesn't work.
Click to expand...

Buying in quantities that don't make sense, doesn't make sense... large or small...... but, again, as you so correctly note, everyone is different and everyone can take TFP as the ultimate raw material and craft whatever pool care they wish and/or need.

Thanks for giving us a venue to share our combined experiences. I know I have learned a ton here and I hope that some of my limited experiences may provide help or inspiration to others.
 
Does anyone else notice a difference in result when using the DPD only test vs the FAS-DPD test? When the result from the powder test is below 5 ppm, so no diluting.

Since I got the powder test I have compared results on 2 or 3 occasions and typically get a smaller FC reading from the color match test by about 1-1.5 ppm.

Any ideas what can explain this? I should mention that I have a 500 gallon hot tub kept at 98 deg. No pool.

Side note I appreciate the direction this thread has taken I'm learning a lot lol.
 
With DPD only drops, it's very important to make sure you're getting well formed drops and that you hold the comparator block up to a bright, uniformly lit background (I use white paper). Indoor lighting is really bad for color rendering.

I have found I can get the two tests to match within a ppm or less difference.


Sent from my iPhone using Tapatalk,16k gal SWG pool (All Pentair), QuadDE100 Filter, Taylor K-2006
 

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