The usual RV water pumps are supposed to self-prime
over a reasonable height; the ShurFlo in my Boler
sits on top of the floor, and the tank is under the floor, so it's pulling the water up about 20 cm (8"), and it doesn't have a problem with that. I don't know if they can handle the height of the portable container.
Newer RV water pumps are available with variable-speed
controls, so they run only as fast as they need to to match the water flow required - this means they don't cycle on and off annoying or need an accumulator; I'd get one of these if I had to buy a new one.
There are some small pumps which are submersible
- they sit in the bottom of the water tank, lowered in through the opening trailing an output hose and a (waterproof) power cord. I use a larger version of this to pump water out of rain barrels. If you can get one small enough to go in the container opening yet strong enough for the desired water flow, this could eliminate any self-priming concerns and provide a place for the pump. Here's one I stumbled across on a web site: Whale Submersible 921
, for an example; I've never seen this actual unit. Some FiberglassRV members have reported using submersible pumps for portable shower setups.
To avoid running dry
and burning out, a float switch of some sort can be used. Sump pumps (regular hardware store stuff) usually include such a switch, so there's a source of possible inspiration. Nothing shuts off my Boler's pump when the tank runs dry, except me noticing the noise and turning off the switch.
If the pump is only to provide water to the sink faucet, I would consider a foot pump
- it keeps your hands free, takes no power, and discourages wasting water by leaving it running. This is not commonly used in landlocked RVs, but is found as a marine item - I've only seen one on a sailboat. I found one at West Marine: Gusher MarkIII Cabinet Mount Foot Pump
, but I don't know anything about this specific unit; it's just to show the type of device, although this one does seem to have about the same pumping rate as my Boler's electric pump. Here's the manufacturer's page for the same pump: Gusher Galley Mk 3
; they have some other options in their Marine - Manual Pumps list
. Maybe one of the more nautical members can provide more useful comments on this possible alternative.