I left my gas can outside in the rain last night (smart!) containing race gas and premix oil. I left the small vent hole uncovered. I'm not sure but a small amount of water may have gotten in there. How big of a deal is this??
Water in the gas isn't good. The easiest way I have found to get it out of a can like that is to let it sit overnight so all the water settles to the bottom of the can. Water is heavier so it always sinks to the bottom.
Without shaking the can at all, slip some clear tubing into the can until it hits the bottom. Start a siphon by sucking on the end of the tubing. It helps if the tubing is long enough so you can see the gas coming before you get a mouth full. Make sure the tubing stays at the bottom of the can and let it run until only gas is coming out.
If you did it right you will have drained out all the water that settled to the bottom and left the gas nice and moisture free. :)
Let it sit, then pour it slowly into something you can see into(five gallon pail). The water will come out last. Dispose of the last half gallon or so, drop a rag into the can and mop up the bottom of the can. Then pour your fuel back into the can.
KAR products makes water traps that you drop into cans/tanks that grab the water up in polymer pellets. They are disposable, once the trap is full you throw it out and replace it.
you need to buy a funnel from RACOR. it has a water seperator element in it and it is safe to use on gas, mixed gas and diesel. believe you me this thing works. i bought one a little iffy if it would keep the water out so i filled it up to the top of the funnel with water and not a drop came out the spout.