As long as you use a float valve on the
DI container, you won't have to have a valve to switch from
RO to
DI. It will automatically keep everything full. You will need to have two containers...one pressure tank for drinking water and one non-pressure tank for
DI water. I use a 55gal food grade plastic drum. You'll have a check valve on the
RO drinking water pressure tank that will keep it from backflowing into the
DI chamber. When you pull some water from the
DI, the float valve will actuate the shut off solenoid and refill it till the float shuts it off again. You could set it up with a T valve, but the automatic system would be much easier on you.
Which adapter you use depends on where you intend to put the system. If you want it under your sink, you should be able to remove the line going to the cold side of the faucet. Screw the adapter on the end of the shut off valve for your sink and reattach the line to the faucet...no cutting anywhere. Another option would be to use the garden hose adapter and mount the unit close to your washing machine. Buy one of the Y hose adapters at the hardware store and put it on the valve for the washer. Attach the washer line to one side of it and the
RO/
DI unit to the other. You could still mount the
RO drinking water tank under the sink. You'd just have to run the small line through the floor and back up into the kitchen where the tank is. That way, you don't have the unit crammed under the cabinet taking up space you need for other things. It's also mounted out in the open which will make filter changes easier. You can get the Aqua FX Barracuda drinking water kit with both tanks from Aqua FX, from Darin at Captive Reefs, or from me...we all carry it. If you're looking at a different brand of unit, any of us can probably get you the needed fittings to set it up this way.
HTH.