I use a 5 gal bucket for my 20G AIO with a osmolator ATO, my 40B uses a gravity fed float valve. I fill the 5 gallon jug about every 5 to 7 days on the 40B via my RO/DI filter, its a bout a 20 foot walk with it. The 20G can go 3 to 4 weeks with 5 gal of RO/Di
