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Thread: Question about chlorine DPD powder

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    Question about chlorine DPD powder

    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
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Mod Squad kimkats's Avatar
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    Re: Question about chlorine DPD powder

    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
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    needsajet's Avatar
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    Re: Question about chlorine DPD powder

    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.
    12k IG salt; glass beads in plaster; K-2006C, K-1766, CCL, and Aussie 4in1 (HTH); Pentair Eco800 1.2HP VS; Zodiac SWC 1.3 lb/day (25 g/hr); 25" filter recycled glass; OKU solar panels; 1/2 HP solar pump; Rebel (Warrior) pool cleaner; FlowViz; prior pool AG 10k | Read Before Posting to get the best possible advice | ... and this helped me a lot!: TFPC for Beginners

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    Mod Squad kimkats's Avatar
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    Re: Question about chlorine DPD powder

    I do clean my spoon out as best I can. I use the end of a sharp knife to scrap the hard stuff out. I then let it air dry.

    Kim
    TFP Moderator 33x52 round AG 25,600 gals Sand Filter 1.5hp Pump - 2 Speed, SLAM, Pool School, Recommended Levels, Recommended Chemicals, Pool Math, Chlorine/CYA Chart, TF-100 Test Kit

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    Re: Question about chlorine DPD powder

    +1 to everything Kim said. All that really matters is that you put in enough powder for the solution to turn pink. Clean the scoop if you like....it makes no difference.
    Dave S.
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    Re: Question about chlorine DPD powder

    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?
    ~12,000gal. plaster, in-ground pool; Hayward cartridge filter; 1hp pump; Use Taylor 2006 kit w/ Speed Stir.

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    Re: Question about chlorine DPD powder

    Mortar and Pestle as in classic pharmacy is what you may want. It really makes no difference, but crushing is fine. Just be careful not to comtaminate it, expose it to moisture etc.
    TFP Moderator
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    Re: Question about chlorine DPD powder

    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.
    16x32 IG Vinyl, 13,000 Gals. Hayward S-244T sand filter, SP2810X15 pump
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    Re: Question about chlorine DPD powder

    Quote Originally Posted by borjis View Post
    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.
    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!
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about chlorine DPD powder

    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.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Question about chlorine DPD powder

    Quote Originally Posted by JoyfulNoise View Post
    If they say to use two dippers full of powder (ever so slightly rounded mound), then use two dippers full
    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.
    JD - 28' Round Above Ground Pool, 17,000 Gallons. Dual speed Jacuzzi pump with cartridge filter. Dual speed 1 HP pump, Hayward S210T sand filter
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    Re: Question about chlorine DPD powder

    Quote Originally Posted by Donldson View Post
    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.
    Agreed. I typically use a 25mL water sample.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Question about chlorine DPD powder

    Quote Originally Posted by JoyfulNoise View Post
    ..... 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......
    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.

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    Re: Question about chlorine DPD powder

    Quote Originally Posted by ewkearns View Post
    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.
    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.
    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Question about chlorine DPD powder

    Quote Originally Posted by JoyfulNoise View Post
    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.
    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.

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    Re: Question about chlorine DPD powder

    Quote Originally Posted by ewkearns View Post
    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.
    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!


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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    Re: Question about chlorine DPD powder

    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.
    Dave S.
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    Re: Question about chlorine DPD powder

    Quote Originally Posted by duraleigh View Post
    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.
    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....


    Quote Originally Posted by duraleigh View Post
    Large quantities of DPD powder to them could be a 10-15 years supply and that just doesn't work.
    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.

  19. Back To Top    #19

    Re: Question about chlorine DPD powder

    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.
    Intex 15'x48" AG metal frame pool (4,440 gal), Krystal Clear (1600) 14" sand filter, Taylor K2006 test kit, Intex Deluxe Maintenance Kit/vacuum (love it!), Intex Deluxe Skimmer, BBB.

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    Re: Question about chlorine DPD powder

    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.


    Matt
    16k IG PebbleTec pool, 650gal spa, spillway and waterfall, 3HP IntelliFlo VS / 1.5HP WhisperFlo, Pentair QuadDE-100 filter, IC40 SWCG, MasterTemp 400k BTU/hr NG heater, KreepyKrauly suction-side cleaner Dolphin S300i robot, EasyTouch controls, city water, K-1001, K-2006 and K-1766 test kits, Mannitol test for borates

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