Water vs. Sodium

So, I have been wondering something for the longest time. "They" say that it's possible to flush some of the sodium out of you body when you drink lots of water. Like if you go wayyy over your sodium one day, the response that is usually given here on MFP is to drink lots of water. First of all, does this really help? Why? And, second of all, if it does really help, I want to figure out how much water is needed. For instance, if I go over my sodium by 2000 mg (cough like today cough) is there a certain number of cups that is gauranteed to flush it out of my system? Is there any type of ratio that anyone follows? I'm very curious to hear from other people on this. I tend to go over my sodium more often then not and I always sit and wonder how much water I'm gonna need to fix the problem. Do I just wait until my pee is clear?? idk! Any thoughts are welcome. I hope this doesn't classify as a stupid question!