auto-filling top-off resevoir

[kwirky]

Hey, hopefully somone can help out.

I've been trying for a while to find plans for an auto-top off resevoir I saw a while ago. It's designed to hold 5 gallons, and has a divider and an airline check valve that makes it fill only when it's empty. It's designed to prevent TDS creep.

anyone seen the thread? I'm trying to remember how it was built and can't.

Even better, anyone have any other good suggestions to prevent TDS creep when hooking an RO/DI straight to the tank?