I'm starting to think I don't know how to do the DPD test, although when I get an unusual result, I typically pull another sample from a different part of the pool and it always comes out the same.
Anyway, I've been shocking my pool for a week now...I haven't done the best job of it because I've got 3 kids, a full time job, and my wife was running in the election last week so pool time was at a premium. posting.php?mode=post&f=10#
Anyway, I'm getting what seems to me to be some crazy results on the FC/CC test and I'm wondering if I'm doing it wrong.
Here's an example...I tested after dark on Friday night...FC=15, CC=0. Brushed the heck out of the pool. Went to bed. Saturday morning I tested at 9am and got FC=2.5, CC=12.5. Holy **** that is a big swing, but I guess it kind of makes sense if I'm fighting a lot of algae. So I ran to the pool calculator and it told me to use 2.3 gallons of my 10% bleach to get back to shock level. So I added 2 gallons (not 2.3) and then headed out with the family. Didn't get back until 2pm. Tested @ 2pm and got FC=22.5, CC=1.5! There's no way 2 gallons of bleach could raise my FC 20 ppm. I pulled more water and got the same result. The filter has been running 24/7, and I'm pulling from several inches under the surface.
The same thing happened Sunday...I tested in the morning and found FC=5, CC=20! Put 2 gallons of bleach in and a few hours later I got FC=25. Now I'm freaking out that I'm going to bleach my liner worse than it already is (previous owners did a number on the 10 year old liner already).
1 question I have on the DPD test...sometimes when I test FC, the water turns completely clear. So I put the lid on the dropper and reach for the R0003 reagent and by the time I do, the water is back to a very slight pink. I know I've read that the water will turn back to pink if you wait a while, but this is only a matter of 10 seconds. Is that the problem?