Using your existing chemicals is fine. Actually, using pool store chemicals is fine. What pool school and really the entire site is about is taking control of your pool. I think the main focus of our site, is not BBB, but understanding the chemistry of the pool.
Above all else, the thing you should walk away with is to test your pool regularly. Like everyday regularly. The chemists on this board are not so fond of test strips (and thus some pool stores because that is what they use) but favor regeant testing. If you cannot swallow the $80 kit right now, and I understand, try to at least go to walmart and buy a $20 kit. It should test all the things you need, the only caveat is you can only test chlorine to 5 - and you really need to test higher. We have ways around that.
If you know where the levels need to be for your pool in the areas of CL, PH and CYA, then by testing daily, you can tell if you need to correct these amount. By correcting a level before it becomes a problem is a lot less heart ache, time and money, than if you let it slip. the other levels, CH and TA are also important, but don't need to be tested as often.
The chemicals you use to correct these levels is up to you. Just be sure of what you are adding. The BBB method simply corrects the problems of our pool with the purist forms of the chemicals needed. More often than not, this is less expensive. All the time, we do not worry about what else we may be subjecting our pool to. However, if you decide that traditional pool chemicals are the way you want to go, there are a number of knowledgable people on this board that will help you get the right chemicals to keep your pool beautiful. Often times buying a pool store chemical to resolve a problem adds problems to your pool that you didn't have before. Thus we ask that you proceed with caution.
We all are very proud of our method of pool care and excited about how great our pools look. Therefore if we appear to be overzealous, it's because we are! Every one of us have virtually nonproblematic beautiful pools. And all we want is for your pool to be the very same way
