How often should I wash my dreads? - Dreadlocks FAQ's
How often you wash your dreads depends on several things, the age of your dreads, your lifestyle, and your personal preference. Newer dreads are more delicate, and while washing mature dreads won't hurt them a bit; washing newbie dreads can loosen them a lot. If you are wearing rubber bands on the roots and tips of your dreads, which I highly recommend, especially while they are new, you don't have to worry about them nearly as much. You should never let your dreads go more than a week without washing. Most people find it comfortable to wash mature dreads every other day or every 2nd day. If you are very active and sweat a lot you may find it necessary to wash your dreads every day. You can also just rinse your dreads after running or other sports.
Since the dreads are most delicate during the first month you're going to be putting in loose hair after every washing. This totally normal and it's actually a good thing since the hair was eventually going to slip out eventually and now you have a chance to dread ball it and get it stuck deep in the dread where it won't ever pop out again. Because the dreads are so new the first month the amount of hair that pops out can be a bit overwhelming...especially if you have like 100 dreads. For this reason a lot of people wash their hair every 3 or 4 days for the first month, then starting the second month they bump it up to every other day or every second day.