Our rig does not have gravity water feed, but a 12v pump works well with a Water Bladder or Jugs. A Water Thief needs an extra hose clamp at both ends under high pressure. Some faucets are threaded on the inside, pipe nipples to a hose thread works well. A dishwasher to garbage disposal connector will work fine on low pressure only. It is designed for low pressure. The sidewalls on a water thief are thicker than the gd connector.
I have never figured out why government parks use non-threaded faucets, knowing people will figure out a method for getting water. I've seen a lot of water wasted in the process.
'04 Newmar MADP, 1100w of solar, towing a lifted Rubicon