Just trumping here, but you might want to look at the mounting of your existing pump. If mounted solid to a surface, the vibrations of the pump will act just like a magnet in a speaker. Any flex in the lines hooked to pump? If not, the lines can carry the noise, vibrate another "speaker"
Stand of and look at your rig from the side. Is your fresh water tank below the floor of trailer? Is trailer floor below floor of TV bed? Trailer have a gravity fill for the tank, where you can pour water in, or must it be under pressure? Assuming gravity fill, can you slide a hose in far enough to get below the floor of TV? Even if you need a short piece of smaller hose to fit in the fill, just screw together so it doesn't leak. Hose from bottom of transfer tank, into fill. Might need a little air pressure in top of tank (fresh water? Bell, just suck the hose!) to start flow, but siphon can move water pretty easy
