DPD powder

[gldungan]

I just opened a new bottle of dpd powder. I put in two scoops and begin adding drops of fas-dpd reagent. The pink disappears around 2.8 but the water is cloudy. I think my numbers look OK and the water is crystal clear before I put in the dpd powder. I have been testing my water for more than 3 years and I have never seen this problem. All my reagents and powder are no more that 4 months old.

Is this power bad? The color is just off white and it's not clumpy

CL 2.8
CC 0
pH 7.6
Alk 90
Cal 330
cya 55
Gunite pool with SWG 18,000 gallons, 85 F

Any thoughts would be greatly appreciated.

Gary

[CarlD]

The pink disappears around 2.8 but the water is cloudy.

CL 2.8
CC 0
pH 7.6
Alk 90
Cal 330
cya 55
Gunite pool with SWG 18,000 gallons, 85 F

Any thoughts would be greatly appreciated.

Gary

Gary,
Your chemicals are FINE: If you check the Best Guess table you will see that for a CYA over 55 you should maintain a MINIMUM FC of 5ppm--that's probably your problem. 55 is a funny number--I assume it was halfway between 50 and 60--that's actually higher--like 58 or so--and figuring 60 is safe.

Best guess says if your CYA is 30 to 50, your FC must be 3 to 6 and shock to 15ppm. If your CYA is 60 to 90 then your FC must be 5 to 10 and shock to 20ppm.
I tend to keep my FC at the same end as my CYA (30 implies FC of 3 or 4, 50 implies 5 or 6). It's not exact--it's a BEST GUESS.

Conditions over the years can change in your water, especially if you haven't had a kit like the PS-23x series, you wouldn't realize it.

My suggestion, to start, is that you shock your pool. Shock it to between 15 and 20--and keep it there until the water clears. Run the pump 24/7 during this. Then let FC drop to the 5 to 10 range. If THIS doesn't work then we can go to plan B.

You only need enough DPD powder to turn the water nicely pink. Any more just wastes the powder--it doesn't turn it pinker. It seems weird, but that's how the stuff works. For the higher FC ranges, just use the 10ml test--you'll save reagent and being within .5 on your FC is enough. Actually, it's usually enough all the time!

[KurtV]

Gary,
Are you saying that just the water in the comparator tube is cloudy and even then only after you've added DPD? If that's the case, I can't offer a very informed opinion but would guess that it's still working OK so long as you're getting the color changes.

If the water in the pool is cloudy (which I don't think you were saying), this article by Ben may help: http://www.poolsolutions.com/gd/cloudy.html

[gldungan]

Kurt,

Yes the water is perfectly clear at the start, then I add the DPD powder, shake and the water becomes pink. Then I start adding the R-0871 and the pink goes away but the water is not as clear as it was at the start. It's not really milky it's just not clear. When I add the DPD #3 reagent to the cloudy water in the comparator the color of the water remains unchanged (no hint of pink) just the same cloudy water.

My pool is very clear. One can read the writing on the main drain covers from the jumping rock.

I appreciate you input. I guess I will continue to use the powder until either someone makes a case to do otherwise or I need to order more reagents.

Gary

[DavidD]

Kurt,

Yes the water is perfectly clear at the start, then I add the DPD powder, shake and the water becomes pink. Then I start adding the R-0871 and the pink goes away but the water is not as clear as it was at the start. It's not really milky it's just not clear. When I add the DPD #3 reagent to the cloudy water in the comparator the color of the water remains unchanged (no hint of pink) just the same cloudy water.

My pool is very clear. One can read the writing on the main drain covers from the jumping rock.

I appreciate you input. I guess I will continue to use the powder until either someone makes a case to do otherwise or I need to order more reagents.

Gary

So it is the water in the test vial that is cloudy. I believe this is normal. If your DPD gets a dark gray, clumpy or real grainy then those are signs it may be going bad. Don't worry and keep testing...

DAve

[Jakebear]

You only need enough DPD powder to turn the water nicely pink. Any more just wastes the powder--it doesn't turn it pinker. It seems weird, but that's how the stuff works.

I was having problems with getting any CC results using my FAS-DPD kit. When I called Taylor Technologies technical service, they told me that the amount of powder used is important.

Being a skeptic (and Cheap) I ran some tests. I ran the same sample 8 times --- 10ml 1 scoop, 10ml 2 scoops, 25 ml 1 scoop and 25ml 2 scoops. The results consistently gave more accurate results (less variation) when two scoops of the powder were used. The difference was 1.8 ppm higher when using the preferred (by Taylor) method using the 25ml sample size. I did the same routine over again --- the results were repeatable!!

Thought you would want to know!!

[DavidD]

So when you say 2 scoops, what scoops are you referring too, Ben's scoop (White) or Taylor's (Blue)?

Dave

[atwetzel]

And are those level scoops, rounded scoops, heaping scoops?

[Jakebear]

Taylor scoops (blue) --- Level

Edit --- Didn't know there was more than one since Taylor makes the reagent.

[cwstnsko]

I've seen both scoops, The poolsolutions scoop is much bigger than the taylor. I've tried the 10 ml test with 1/2 and whole scoops of Ben's scoop, and the test was the same for normal levels of chlorine. If I'm measuring shock level chlorine, I make sure I get a whole scoop just to be safe