DPD (no FAS): the longer it sits the pinker it gets

Jump to latest Follow Reply
F

fathom39

0
Oct 17, 2010
28
After putting in the 5th drop of R-0002 and shaking, the color barely registers on the border of 0.5-1 / 1-2. But, if I let it sit five minutes or so it darkens and get to the 2-4 / 3-6 range. Which is true - the immediate color or the later color? OTO always seems to validate the 2-4 / 3-6 range.
 
What are you getting for CC? After adding the R-0002 and reading the level, then you add R-0003 to see how much darker it gets to determine the CC (combined chlorine).

You're only reading FC with what you're doing. The OTO reads FC (free chlorine) + CC, which equals TC (Total chlorine). You probably have high combined chlorine or it's a result of MPS.

Are you using MPS (non-chlorine shock)?

You really need to get an FAS-DPD test kit.
 
Do you by chance have a Leslie's kit? Is it new?

Those reagents are what was used in the Taylor K-2005. They work, but the DPD test is so much better. No guess work, and all you do is count drops. Color matching isn't easy for me although I did use that test all of last year and into this year with success.

You can always order a DPD kit and then you'd have what you need. The nice thing about the R-0001 and R-0002 reagents is that they are reds. I like reds better than the yellow of the OTO but neither tests above 5ppm. DPD is the way to go for sure, unless I am sure the pool is low I use the DPD.
 
There is a bleed-through of CC into the FC test for DPD if you wait too long -- more than a couple of minutes or so. Nevertheless, FAS-DPD seems to be more accurate than DPD regardless, at least when using a visual comparator for DPD.
 
If I let mine sit for a while, I do see a tinge of pink. Not so much though, just a tinge.

On the other hand, I let the sample sit for about 1 minute at dad's the other day and it turned hot flaming pink.

I took that to mean he was on the ragged edge of ok. Very suspect IMO.
 
Thanks All,

Yes, I use Leslie's basic DPD kit (R-0001, R-0002, R-0014) for FC testing and the HTH 6-way kit for TC and then using grade school algebra I can determine CC. :-D Someday I will get a "proper" kit but I think for now it would only get me FAS and a rather useless acid demand test over the kits have now. Also, I'd rather use that money towards an upcoming RO service to remove excess calcium that was detected by my inferior kit. Enough about kits and sarcasm.

So, now my pink and yellow levels are almost equal upon initial reading. When at first I was getting almost no pink, I worried and ran off to Costco for a bunch of bleach. I avoided setting the SWG to "super chlorinate" because I didn't want to stress the device. I normally run it somewhere between 45 and 65 percent. I never used the bleach and now without explanation my levels are almost equal and in fact a little high.

Questions:
Does a SWG system catch itself up by constantly producing FC such that CC just withers away over time? Ca CC be destroyed only by shocking?

TC 5
FC 5
pH 7.5
CYA 70
TA 80
 
CC actually gets created when the FC is getting used up. In an outdoor pool CC gets destroyed by UV from sunlight. If you let the swcg run and there's not a lot going on in the pool it can "catch up" over time. That doesn't normally happen because once algae gets started it reporduces exponentially and the chlorine production can't keep up with it.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply