Though this isn't the problem you had the X3 is notorious for springing leaks in the washer fluid pumps that are on the washer tank under the hood. My 2006 drained all its fluid and then again after about week once filled. Replaced the pump that was leaking, and to help others that may come across this i created the following tutorial/photo document of the replacement:
BMW X3 Washer Fluid Pump Replacement DIY
You can fix it for about $35 in parts and save a ton of money over what the dealer would charge I'm sure.