For several years now we have been catching rain water via our decks while at anchor. We have tried many different ways of collecting rain water, but simple is best. First we allow it to rain and wash the salt off the deck, then we go on deck and using a chamois and a weight like a winch handle we will make a dam at the water fill. The IP deck has a raised edge which will funnel the water right into the fill cap. All that is needed is a way to stop the water with a deck dam. The chamois soaks up the water, and sticks to the deck, and the winch handle add the needed weight for floods. With a good rain, the tank will pick up many gallons. If it becomes full, we fill 5 gallon jugs via the cockpit shower hose. If nothing else, it a fun activity on a hot summer rainy day.
Here is a video of this process:
ipyoa.com/index.php?option=com_seyret&It...ideodirectlink&id=18 
