I'm thinking about getting a reverse osmosis water filtration system because i'm getting tired of filling up gallons of water off my tap at the house and taking them over to my friends where we brew. We would filter the water there off his sink but he is on well water and there seems to be a lot of calcium in it even after a regular water filter. We are making 10gal batches and the only reverse osmosis filtration systems i've seen only have 3.5gal tanks but i haven't seen how fast they fill up. Anybody out there have any suggestions on this.