Plan on having water in your tanks!  I had 900+ hours on the RV6 with no water in the system after washing and occasional overnight tie down with rain.  Then, last AirVenture with several rains during the week, we had a little water in one tank.  After much shaking and sloshing we got a little more.  At the first fuel stop we had over an inch of water in the fuel sampler from the gascolator and more from the one wing tank.

 

Another consideration is water that passes from the tank to a low spot in the fuel lines.  Since water is heavier than fuel it will accumulate in that low spot unless you find a way to drain it.  I opened the drain valve on the gascolator and ran about 10 oz of gas on the ramp with the boost pump and got a few more water beads.  

 

Steve Colwell   Legacy