I get 20 liter (actually 19 I think) water bottles refilled for $10 pesos. The shop has a reverse osmosis system and is a block away. I have a wheeled cart to carry the water bottle. It doesn't save a lot of money, but the place is in a mercado where I shop for groceries most every day anyway, so it is not much extra effort to take a bottle in to be refilled. Some people prefer the bottles filled at a factory. I would just as soon have them washed and filled while I watch.That's an interesting question...I wonder if Home Depot in Mexico sells any RO systems? My mother-in-law has 20 liter bottles of "Ciel" water delivered for 24 pesos per bottle. For that price, an RO system might not be economical. Good Luck!