1 bong hit will probably be gone in 7-10 days. You can buy a 5 pak of test kits off Ebay for a very reasonable price. Take a test at 5 days and see how quick it turns positive. If its real slow to indicate and very faint you are most likely going to be fine in another couple of days.

I have cleaned out after smoking 2-3 times a week in as little as 10 days and no longer than 14. Similar height & weight.