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Thread: Does R-0870 (DPD powder) really expire?

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    Does R-0870 (DPD powder) really expire?

    Bought a huge thing of it a couple yrs ago. Expiration says 7/16. Still works but can I trust the results?

    30k gal, IG, vinyl, Pentair Tagelus TA 60D sand

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    Re: Does R-0870 (DPD powder) really expire?

    Also my R-0871 says it expired last June.

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    Re: Does R-0870 (DPD powder) really expire?

    The liquid drops should be replaced. As long as your powder isn't brown/black or has been exposed to moisture, it should be good to go. Crush it up if it's clumpy. As long as a standard scoop size turns your test water a nice pink.
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    Re: Does R-0870 (DPD powder) really expire?

    What happens to the liquid? It still dilutes the pink.

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    Does R-0870 (DPD powder) really expire?

    Quote Originally Posted by aralph View Post
    What happens to the liquid? It still dilutes the pink.

    Sent from my MotoE2(4G-LTE) using Tapatalk
    The reagent is ferrous ammonium sulfate. It is a reducing agent. The reducing agent can get oxidized by absorbing atmospheric oxygen over time. If that happens, it's ability to reduce the dye from pink color to clear will be diminished and you will get a false high reading.

    Reagents really should not be bought and stored in large quantities. The savings incurred are basically pennies per test and the uncertainty caused by expired reagents is not worth it. There are ample suppliers online and, in most cases, the chemicals can be procured in less than a week. A typical [EDIT] 10 gram [END-EDIT] bottle of R-0870 and 2 oz bottle of R-0871 should easily last a full season.

    The powder can go bad too. The DPD dye is only a very small proportion of the overall mixture (< 2%). The rest are pH buffering agents, metal chelating agents and deoxidizing compounds. They can all go bad and give spurious results.


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    Re: Does R-0870 (DPD powder) really expire?

    Thanks. What about CYA regent? Does it expire? I tested at 50-55 a week or so ago then 40 yesterday. No drain just rain.

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    Re: Does R-0870 (DPD powder) really expire?

    As long as it is stored in a cool, dry environment, R-0013 reagent takes a very long time to go bad. Often times a difference in testing can be attributable to a difference in lighting from each day of the test, cold water, or simply a +/- 15 variance in that particular test. If you don't do it already when conducting the CYA test, take several readings with the same mixture by reading once, then pouring the tube mixture back to the mixing bottle. Re-test and do that 3-4 times to get a good average.
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    Re: Does R-0870 (DPD powder) really expire?

    Depending on storage- ideally in a cool dark place inside, you should be able to squeeze 2 swim seasons out of your reagents.
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    Re: Does R-0870 (DPD powder) really expire?

    I can attest it wasn't stored inside. So maybe I can't trust any of my regents at this point.

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    Re: Does R-0870 (DPD powder) really expire?

    In that case, get new reagents, and toss the old ones. Your results are worth the money no matter how it turns out.

    Proper results provide huge value for the dollar considering the large investment of a pool they are protecting, and they dont cost that much. In terms of value, it is no different trying to save money by using cheap or questionable motor oil in a nice new car. You simply wouldn't do it and be wise in choosing that plan.
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    Re: Does R-0870 (DPD powder) really expire?

    Is it ever common to get a high CYA reading immediately after an add, only​ to have it come down to a more predictable level a week or so later? I was very surprised by the 50-60 reading I got right after the add given the amount of CYA I added (3 lb to a 30k pool with a start of 20 CYA). So the 40 I'm getting makes a lot more sense. I was basing my SLAM levels on the 50 but my results (18 days and counting) have been very poor thus far.

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    Re: Does R-0870 (DPD powder) really expire?

    Starting at 20 ppm CYA and adding 48 oz gives you an ending 32 ppm CYA. There is no explanation for how you tested and got 50-60 or how you are getting 40 right now.
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    Re: Does R-0870 (DPD powder) really expire?

    Quote Originally Posted by aralph View Post
    Is it ever common to get a high CYA reading immediately after an add, only​ to have it come down to a more predictable level a week or so later? I was very surprised by the 50-60 reading I got right after the add given the amount of CYA I added (3 lb to a 30k pool with a start of 20 CYA). So the 40 I'm getting makes a lot more sense. I was basing my SLAM levels on the 50 but my results (18 days and counting) have been very poor thus far.

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    Quote Originally Posted by duraleigh View Post
    Starting at 20 ppm CYA and adding 48 oz gives you an ending 32 ppm CYA. There is no explanation for how you tested and got 50-60 or how you are getting 40 right now.
    20ppm CYA is really too low to practically measure. I know the tube is labelled that way, but I doubt anyone can see the difference between 20 and 30ppm CYA. Therefore, you could have been much closer to 30ppm, added the additional 12ppm of CYA and are now at 40ppm which is what you are seeing.

    Could you possibly have scooped up some high CYA water that had not fully homogenized...I doubt it but it's certainly possible. More then likely the 50-60ppm was an operator error with lighting issues being the usual suspect.
    Matt
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    Re: Does R-0870 (DPD powder) really expire?

    Here's exactly how it played out. Added CYA to skimmer over several days via a sock. Took measurement at 50-60. Read several days later about the waist high glance test with back to sun. So took another and got same reading at around 50 or 55. Took it again yesterday (and again today) and got 40. It rained a couple of times and I've added probably 60-80 gallons of bleach over the past 18 days. I added water once to make up for a little loss.

    30k gal, IG, vinyl, Pentair Tagelus TA 60D sand

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