For me, I gain up to two pounds (it's getting better, used to be four) and it drops off a few days after my TOM ends. If I record my weight while retaining water, I always put a note next to it so I remember it's not real weight gain nor real weight loss.
I really appreciate all your answers. I'm sort of new to this whole "scale" thing. I don't get on very often (to avoid obsessive behavior). I looked through past threads to try to find an answer, but no one seemed to ask this particular question.