I use a 55gal chopped down to 40ish for an RO res. Have it sitting as close to the ceiling as I can get it. Float filled from RO gravity drain. Poor RO has to make plant and beer brewing water LOL. I just use a garden hose brass ball valve fitting. Pipe thread into the bottom side of the barrel. Not a 90 45 maybe. Goes from barrel to UV then a have another plastic ball valve on the end to pull water from.