Really inconsistent FAS-DPD test results! HELP!!

[thefloatqueen]

Hi, y’all! I’ve been using the TF-100 test kit and the speed stir since I got my first pool in 2019, so I’m no stranger to the FAS-DPD powder test for testing my FC. Up until this year, results have always been very consistent, give or take maybe .5 ppm. This year, totally different story. For example, I’ll get 8 ppm the first time, and 9.5 or 10 ppm the second time. The only consistent thing is zero CC. I’ve been testing twice (or several times) because something feels off. It is really frustrating and sometimes I’ll take the average of my tests and put that in my PoolMath app.

Could it be that I’m not using enough powder or the amount of powder I’m adding is a little more or less than the other tests? I’ll admit, sometimes there is a little more or less than previous tests. I really didn’t think it mattered as long as I fill the scooper and the water turns pink. I don’t really do the “heaping scoop” as I’ve been told here that it’s not necessary to scoop a huge amount of powder — but I’ve also been doing it the same way for years lol. All of my testing reagents are brand new that I ordered from TFTestkits in March during the sale. Could this just be a bad batch of one of the reagents for the FAS-DPD test? Water temperature? Recently increasing my CYA?

I really would like to get accurate, consistent FC readings with summer being right around the corner. All of my other tests are consistent, why not this one? Ugh, so annoying. Thanks in advance!

 

[Newdude]

Could it be that I’m not using enough powder?

If it goes good and pink, and has one or two grains swirling around undissolved, that's perfect. Any more is a waste of supplies.

I’ll get 8 ppm the first time, and 9.5 or 10 ppm the second time.

I've been guilty of rushing many times myself. Anytime it's fishy, I slow it down and really pay attention. It's usually within .5 after that, which is the acceptable test variance. And besides, the 8 or 9 is GREAT for most CYA levels. A 2 or 4 wouldn't be. So as long as you're on the good side of the fence, don't sweat the small details.

Keep in mind too, any test is just a momentary snapshot of that part of the pool. It can vary some a few moments later, or from this side to that side at the same moment. Above grounds also are handicapped from less than stellar circulation, even with the pump running. Focus on the part about ensuring you have enough FC left to make it to your next test/dose, and the finer details matter less.

 

[thefloatqueen]

If it goes good and pink, and has one or two grains swirling around undissolved, that's perfect. Any more is a waste of supplies.

I've been guilty of rushing many times myself. Anytime it's fishy, I slow it down and really pay attention. It's usually within .5 after that, which is the acceptable test variance. And besides, the 8 or 9 is GREAT for most CYA levels. A 2 or 4 wouldn't be. So as long as you're on the good side of the fence, don't sweat the small details.

Keep in mind too, any test is just a momentary snapshot of that part of the pool. It can vary some a few moments later, or from this side to that side at the same moment. Above grounds also are handicapped from less than stellar circulation, even with the pump running. Focus on the part about ensuring you have enough FC left to make it to your next test/dose, and the finer details matter less.

Thank you!! I also realized sometimes the drops come out quite fast in the beginning. They are usually the same size but sometimes the first 5-6 drops are one right after the other. The second test they sometimes have a few more seconds between drops. I can’t believe after all these years of OCD water testing, I’m struggling with one of the easiest tests LOL! I could understand if it was the CYA test but sheesh lol

 

[Newdude]

I can’t believe after all these years of OCD water testing, I’m struggling with one of the easiest tests

Worry not, your Majesty, if it's a 9 or a 10. Instead, celebrate that today you have enough FC to lasteth until tomorrowth. Pass a proclamation that today is 'Enough FC day' and all is splendid in the kingdom.

 

[thefloatqueen]

Worry not, your Majesty, if it's a 9 or a 10. Instead, celebrate that today you have enough FC to lasteth until tomorrowth. Pass a proclamation that today is 'Enough FC day' and all is splendid in the kingdom.

That’s PART of the reason why I’m keeping it so high lol. That way if my testing is wrong, I at least know I have at least the minimum for my CYA lol

 

[Mdragger88]

Slow but steady, consistent, big drops- don’t squeeze the bottle. A drop per second is about right. I do a slightly heaping scoop of powder for normal fc levels & 2 regular scoops for slam/high fc levels to ensure there’s enough- more is ok (although wasteful) less or not enough could give you a falsely low reading.

 

[thefloatqueen]

Slow but steady, consistent, big drops- don’t squeeze the bottle. A drop per second is about right. I do a slightly heaping scoop of powder for normal fc levels & 2 regular scoops for slam/high fc levels to ensure there’s enough- more is ok (although wasteful) less or not enough could give you a falsely low reading.

Thank you! I’ll go with the “heaping scoop” from now on. I’ve never heard of anyone using two scoops. Is that for the 25 mL FAS-DPD test?

 

[Newdude]

I used to need a rounded 'snowball' of a scoop for 10ml. (Aka heaping scoop or double scoop) The new kit works fine at a mostly level scoop. Adjust as necessary to ensure there's a little powder that didn't mix to know you're using enough.

 

[thefloatqueen]

I used to need a rounded 'snowball' of a scoop for 10ml. (Aka heaping scoop or double scoop) The new kit works fine at a mostly level scoop. Adjust as necessary to ensure there's a little powder that didn't mix to know you're using enough.

I usually notice a few “crystal”-like pieces on the bottom but it’s not something I regularly pay attention to. I had no idea that it even mattered! Wow, learning something new every day. For what it’s worth, I try to dig out as much “powder” without clumps as possible until I start getting low and have no choice lol

 

[Jonsstihl]

thats funny I usually try to use up the clumps first. I don't think it really matters but what I noticed with my test for the first time is that the solution would turn white then back to pink before the next drop would hit. This is during a slam and I never had it happen before so I am wondering if something is up. or if that is normal when at slam levels. this is my first slam.

 

[thefloatqueen]

thats funny I usually try to use up the clumps first. I don't think it really matters but what I noticed with my test for the first time is that the solution would turn white then back to pink before the next drop would hit. This is during a slam and I never had it happen before so I am wondering if something is up. or if that is normal when at slam levels. this is my first slam.

There’s an algae section (if that’s the reason for your SLAM, which I’m assuming it is) with tons of really helpful members who can answer your SLAM questions. Fortunately, I have not had to do it yet other than raising to SLAM level before closing. I do know if you take too long between drops, it can turn back to pink tho.

 

[mgtfp]

They are usually the same size but sometimes the first 5-6 drops are one right after the other

What helps to avoid this is to pre-squeeze (pushing some air out) the bottle a little before turning it up side down. That creates a slight under-pressure in the bottle and you'll have more control about how fast the drops form.