bobhenry wrote:The water will move at 8 to 10 psi you do not have to get crazy with air storage tanks or anything else.
Okay, but if the water tank starts at 90% full and 30 psi, by the time it is down to 70% full it has about 10 psi... and after that there's not enough pressure to use the rest of the tank capacity.
bobhenry wrote:How about a 12 volt dc power source that will also power your AC tv for up to 4 hours and also has an emergency work light. If your tow has a dead battery get a quick jump and of course if you need an air compressor for a low tire of water delivery just use the compressor. Some time life does not have to be all this damn difficult

If this portable power pack is used to run an electric water pump instead of going the air-pressure route, I agree that makes sense. Of course, if the trailer has a battery already, an electric pump is the easiest solution, and no extra portable power pack is required.
In a system with a powered pump, there is no duplication of faucets or tanks, only the filler. I agree that having one fill point to refill the tank and to stay hooked up while at a serviced campsite makes sense, but you can do that with one cheap valve between the water line from the pressurized water inlet and the tank: hook up the hose, open the valve until the tank is full, and you're done. A float valve (kind of like in a toilet tank) can even make it automatic.
Another way to have running water (in addition to electric pumps, gravity feed from an elevated tank, air pressure, and hand pump) is a
foot pump. Hand pumps are very common in small trailers, and there's already an example above, but of course one hand is kept busy running it; a foot pump leaves both hands free. In a really quick search I only found this
Whale pump, but there are nicer designs available; they seem to be used primarily in boats.