I've had a K&N and a CAI since April of 2000. The filter gets very dirty from all the driving I do, but never does moisture get soaked through. You don't have to worry so long as your intake is not in direct line of sight for water to splash right on to it. It's very hard for water to travel up the hose, which is curved, from underneath the car. I have to clean my filter every couple of months. If you keep it clean and oiled you won't have any problems (remember oil and water don't mix).