With hard water, don't bother with the Dr. B's. You won't see residue build up right away. But over time, you'll notice that your locks are weighed down, and feel heavy and stiffer than they should.
You can keep using the BS wash, but you'll have to do something about the water. You can either start to buy bottled water to wash with. But that gets expensive. Or you can boil it/distill it. Boiling it is easier in the short run. You get a big pot of water, boil it, and let it cool. Fill whatever container you use to mix the BS and water in. But do this GENTLY, and always leave some water in the bottom of the pot. Hard water has dissolved and undissolved minerals in it. When you boil the water and let it cool, those minerals sink to the bottom. By leaving some water at the bottom of the pot, those minerals stay in the pot.
Mix your BS in this new clean water, and wash with that.
You don't need to use the boiled water for the ACV, since ACV doesn't need to dissolve.
Or, better yet, look into dreadlockshampoo.com soaps. They are the best for locks, and pretty local. They are a small company based right outside of Philly. Their prices are great, and they ship really fast. Plus they use flat rate shipping boxes, so you can get about 6 bars/bottles in a package before the shipping rate goes up