Dont run the line in the attic unless you want HOT water in your tank in summer and cold in winter. plus in winter your line could freeze. My ro unit is connected to a fluidmaster toilet valve in a 5 gal bucket and gravity feed to a kent float valve in the sump. Less than 10 bucks to build. Has NEVER failed in the 5 years its been in operation. no pumps, soleniods or electricity. Why make a simple system so complicated with all this other stuff?? PM me and I can show you the SIMPLE way.