I had a response from Joe about an Inquiry I posted yesterday.
To be more clear, the faucet/valve allows water to flow into the sink freely, as soon as the 'city' water is turned on. All 'city' water is pressurized by gravity. My faucet/valve has a 'bale' that turns and holds down the (pump?) lever, I'm assuming this is to secure that lever while traveling. I guess my biggest question is how do I stop the water flow when the campsite valve is turned on outside?
I've found two sources of flooding. One was the sink overflowing when the drain was capped outside. Another was a hose which had no end-cap installed, and was located in the bottom cabinets opposite the sink/cookstove. These shouldn't be a problem in the future.