Moosey, agreed your RV prob has a screen over the freshwater air vent already.
As for lasting the week, I prefer to fill up with good old tap-water (Rather than filtered or spring-water) because I actually want the little bit of residual chlorine from the tap water to keep my trailer water from going south. Check your RV manual or online for some tips about how to flush and store the rig between camping trips to keep the water system clean. However, after the first few days at Bman, I don't drink the RV water anymore. I'll use it for cooking, cleanup, brushing teeth, etc, but I switch to jugs of water for drinking. That's just me, but I don't like the idea of drinking several-day-old water.