If that's all you did, it would take 3-10 days to clear your system.
How Long Does 3 Hits Of Weed Stay In Your System?
Just to be safe, assume that 3 hits would be the same as a small joint. If you do NOT smoke often then 3 weeks to a month will do, if you smoke a lot, then a month to two months, combined with no longer smoking, and "flushing" your system (drinking lots of water) will do.
