The only thing about draining, is if you have metals coming back into the water, you will be at square one again, unless you have a really bad stain problem, then as smallpooldad says, it may be a good option to consider. I just make sure I keep any metal in my water in suspension. You can add the metal free any time. I always add the metal free when I open, when there is a lot of new water in the pool, and whenever I see any staining start to form. I would add it first, then the muriatic acid, you can add them within minutes of each other. If you have a sand or DE filter you can put a puck in the skimmer basket - keep your pump running 24/7. When you add bleach - do not add it in the skimmer if you have a trichlor puck in it - add it in the stream from the return jet. Hope this helps, if you have any other questions feel free to ask.