Top-off pump

[Matt]

I want to experiment with auto top-off of my tank.

There are two methods I'm considering. One seems higher risk, but I'll lay them both out. For aesthetic purposes, and for space constraints, I don't want/can't have any resevoir on the main floor.

1) An sealed kalk jar (a reactor, I guess), with RO/DI output IN, and floatswitch controlling topoff. Essentially a KALK union, using household water pressure to power the lift to the tank. Does anyone do this? I worry about the unlimited input side, of course. I also wonder about backflow when other water outlets are open. I suppose a check-valve would fix that. I know there aren't many who would recommend effectively plumbing the RO/DI directly to the sump this way....

2) An open (unpressurized) kalk resevoir with a lifter pump to the tank. Anyone know an appropriate pump that can lift water 10' or so, but will only pump a gallon or so a day, at what amounts to a drip rate?