When you pump gas in your car is it possible there is water in the gasoline?
Most gas stations have several filters to keep water out but water can get into the gasoline. Yes, it is possible.
Is it possible to cause damage to your fuel pump by waiting til the car is on empty to fill with gasoline?
Is my fuel pump going when there is gasoline leaked under the car and the car sputters while accelerating?
When a water pump is going bad, you change it as soon as possible. You do not want to be stuck alongside the road with your car broken down. You purchase a new or rebuilt water pump. You take the old one off and put the new one on. However, since you needed to ask this question, you take the car to a mechanic and have him do the work.