I bought a better seltzer machine from the soda club. $79 for machine, 2 bottles and 1 co2 tank that weighs 5 pounds and will supply enough co2 for 110 liters of seltzer water. I'm going through about 1 liter a day of seltzer water, plus it's working for ph adjustment. Stay tuned for updates. Otherwise I would spend $365 a year for co2 cartridges. Much cheaper and not much more. The box says 17 cents a liter bottle. Not to mention my aching back to carry home all those bottles.