I would recommend an auto shut off kit on each bucket. If either one gets full enough to trigger the float it will shut off the entire system. (They're cheap)But I live in an apartment. I've seen RO/DI units for fish tank drip systems, but they constantly produce the stuff. I'd need something that I could produce like, a limited amount in a short or pre-planned period of time. I think being in an apartment rather than a house makes this generally difficult.
http://www.bulkreefsupply.com/auto-s...s-systems.html