. . . unless you don't really need it.

I was just making a point about the weight equivalences. In fact, you could almost certainly never save as much weight from the rest of the bike as the weight of a full water bottle. Probably not half a water bottle. And saving the weight of a quarter of a water bottle could cost around $1,000.

Put another way . . . go to the bathroom before your ride and you've lost the equivalent of several hundred dollars worth of weight weenie weight savings.