Actually, I still use my OTO most days to test my chlorine. My pool is well maintained and my chlorine levels are consistently monitored so I know my water is sanitized and I have no CC. So a reading from my OTO kit is fine for me for most days. My CYA is low enough that I don't have to keep my chlorine higher than my OTO kit will read. So, while I do need my FAS-DPD at times, my OTO serves its purpose, too.

Of course, I've been doing this for awhile. If you are new to your test kit, it is a good idea to use it often to become proficient at doing the tests in it. Also, if you are clearing up a green or cloudy pool, you'll most likely be shocking and will need the FAS-DPD to be able to read chlorine readings higher than 5.

Long story short -- even if you have a good test kit (which you should), your OTO kit is still something you will use.