Do I need to rinse or wash my dreads with vinegar? - Dreadlocks FAQ's
Fortunately no, in most cases there is no need to subject yourself to that! =] If you have used soaps or shampoos on your dreads that leave residue they could be used to assist removal but it would not be my recommendation. Our dread soap does a good job of removing most soap residues all on it's own, although it may take many regular washings to remove heavy build up. In cases where you suspect residue build up, or just as a routine deep cleaning check out "How do you give your dreadlocks a deep clean?" . This is an excellent practice.
Vinegar and Apple Cider Vinegar are thought to do a good job removing soap scum (aka soap residue) due to their low ph, so it's potentially helpful for those with build up. The idea is to mix it 50/50 with water and warm it up. Soak your dreads in it for a few minutes, then rinse them very well and wash'em with residue free soap. If you have soap residue build up this will likely remove more of it than washing with dread soap alone.
Some suggest Vinegar as an alternative to shampoo. I don't, simply because it is not a soap or detergent and it doesn't act as an emulsifier, helping the grease and water mix so that the water can carry the dirt and oil away. That's what soaps and detergents do and that's why they are used. On a side note I also find the smell unbearable so I'd never want to put it in my dreads but that's just a personal preference. You are welcome to try it and make your own call.
Baking soda usually comes up too. Baking soda is a weak base. Some suggest it's another shampoo alternative. It has the same problem Vinegar does (lack of emulsification ability) but it also lacks the residue removing properties of vinegar. At least it doesn't make you smell like vinegar which is certainly a plus. Again, it's practically free, so try it if you like. Some people also recommend mixing the two, I used to do that all the time. I'd add some red food coloring and call it a "volcano". Mom always made me clean it up. True story. You might remember doing the same thing. When you mix baking soda and vinegar they react and neutralize each other so you get no benefit from the ph. This doesn't stop people from recommending it. =]
In the end you are welcome to experiment and try anything you like, but it's my personal opinion that a residue free shampoo is the quickest and easiest way to guarantee clean healthy dreads and keep new growth locking fast and tight.