Tank Ro/di & Drinking Water

[TANGOMAN]

I've finally gotten around to installing the water tap in the kitchen and I've hit an obstacle in plumbing it into my RO arrangment.
The 3 gallon reservoir which accompanied the system is simply "T'd" at the output end of the system, correct me here if I'm wrong. This vessel simply supplies a limited volume of drinking water.
I am currently feeding two reservoirs for the aquarium from the RO unit, one for making saltwater, the other is a gravity fed evap. make-up reservoir. A float valve is installed in both reservoirs as well as the gravity fed sump.

If I install the kitchen reservoir with the tanks reservoirs, the limited volume of water for drinking will be shared with the aquarium, correct? This will create a problem as I have the supply water for the RO/DI unit on an electronic valve. It is a simple garden variety timer with adapters on the garden hose fittings. Maybe I'm paranoid but the back up systems have back up systems. The main reason for a timer though is the RO unit does not always "kick-out" when it senses back pressure from the float valves. It was simply passing water through to the waste line. Water consumption was outragious...!

My only solution which comes to mind is a check valve installed on the kitchen water reservoir inlet? Has any one seen these? A 1/4" John Guest style would be the ultimate addition to the rats nest of flexible tubing down there...!

One other thing about the drinking water, should I T in before OR after the DI cartridge?

Thanks in advance!