RO topoff & TDS creep

[Railskinner]

Pictures of top up systems that people use would be a gr8 addition to the thread.
I have a ro/di unit hooked up to a 10 gallon container operated with a humidfier float valve ( bought at HD). Thats as far as i got so far, still taking water from container by hand (syphon)to top up sump.I loose about 1 gallon a day due to evaporation.Ro/di unit starts and doesn't run long replaces what i use, I was thinking of putting another float in sump, hasitante as thinking this would just be a trickle system then from ro/di to 10 gal.container to sump.Might as well went straight from ro/di unit to float valve in sump then.How does one rig container to drop 3 to 4 gallons then kick in ro./di unit.So this then would cause my ro/di unit to kick in about every 4 days creating new water.