Up until this year, I have been using the test kit from Pool Solutions. This year I ordered new reagents and have been fighting a cloudy/algae pool. I ran out of R-0871 and ordered the FAS/DPD refill kit. This kit came with a graduated cylinder. When testing this evening, I used the "old" graduated cylinder and got an FC = 13.5. For some reason I decided to repeat the test with the "new" graduated cylinder and got an FC = 11. Both cylinders have the 10ml level marked clearly on the cylinder (not stickers). So I filled up the "new" one to the 10ml level and dumped it into the old and when I checked the measurement, it only measured barely over 8ml. Obviously, this has created the discrepancy in my test results. The odd thing is that when using the "old" one the pink color was a darker pink and the "new" one was a lighter pink. I am very confused why I would get higher FC levels with more pool water.
How can I tell which cylinder has the correct 10ml level?