Just to add to what previous posters have said......I did not want to (so far) remove the water fill inlet port (e/w vent tube screen and vent line behind it) so I just use a foot long piece of rubber hose (gas line or similar that just fits over the vent line opening on the fill inlet fixture).....and blow air into the vent tube forcing any water back into the fresh tank.
Be careful, if your tank is actually full, as you blow the vent clear of water you may get the overflow water coming back out the main fill tube onto the ground......or your face if you stand in front of it. Ask me how I know that.
If you are actually filling the tank, but having issues getting water into the tank because the vent line has water in it.....blowing through the cheater tube to clear the vent line should allow water fill to proceed without issue. The vent line inside the coach needs to be moved/positioned higher than the fill tube but so far the cheater hose has been much easier for the few times I needed to use it over the last 7 years.
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