I have a tiny Intex, but bought the $25 FAS-DPD kit from Dave, and I'm glad I did. I had trouble knowing if my chlorine reading was 2 or 5 on the hth one, so I like the precision of his. Especially if you ever need to super-chlorinate (the act of shocking your pool), I think you'll appreciate having the FAS-DPD kit - especially since draining and refilling apparently isn't a great option for you. Dave also sells a CYA kit for $17 that has enough for 16 tests, which is way more than a normal Intex user would need in one or even two seasons. Next year, I'm going to save the $20 on the 6-way hth and buy the following:
1. $25 FAS-DPD kit from Dave - which I will use any time I want reassurance on FC versus CC or if I (or my friends) ever need to shock with extra bleach
2. $17 CYA kit from Dave - which I will share with my many many Intex friends so we all know when to stop the Dichlor
3. $5 hth kit that just does chlorine and pH - which I will use daily
That will be the best $47 I could spend to ensure my kids can swim all day every day if the weather permits. And if my friends chip in for the CYA testing, I will get off even cheaper!
Using BBB from the very beginning, I've had nothing but clear water and good numbers. Some friends not using BBB however, with the same pool as ours, recently had very slightly cloudy or dull water - could tell something was "off." With Dave's FAS-DPD I could tell after one test that their CC's were over .5. So, despite the hth OTO kit indicating high chlorine, they actually needed to add more bleach, not less. Couldn't make that distinction using the OTO test. So, again, if draining and refilling isn't a good option for you due to using a well, perhaps just getting the $25 kit is the way to go --- but don't let me talk you into it, follow Dave's advice.