[see attached diagram]I've not yet tested this! Trying to find portable instant hot water systems on line, I thought of this: A thin copper tube coil cone that can be placed over a conventional gas cooker burner. The cold water source can be a tap(faucet), raised storage container, or a pump, like for a 12v camping shower, creating a low-flow, instant hot water apparatus. The addition of the copper coil-cap makes it seem more viable. Anyone know of such a thing? Any advice before I try to make one?