Nice article. SodaStream has found a sweet spot where it's providing a convenience and savings for the end customer, while still making profit hand-over-fist on the consumables, and probably even on the base machine. My family of four probably consumes close to 4L per day of SodaStream output, 70% as fizzy water, 30% as diet soda.
The project on my to-do list (please don't do this unless you know what you're doing) is to cut the top off of an expired SodaStream cylinder and fashion it into an adaptor for the hose from my 5 lb. CO2 tank. 5 lbs. of CO2 will yield something like 500 L of carbonated water, at the same $15 per fill as the SodaStream 60L refills. This should bring the cost down to $0.05 per liter or less. SodaStream will still get my money for their soda syrups, but I can disintermediate their highway-robbery CO2 service.
How much pressure is in the 5lb CO2 tank when it's full? Duct tape probably wouldn't be strong enough.
The canisters look aluminum, so welding would probably be difficult - aluminum is supposedly very difficult to weld, and welding different types of metal is very difficult as well. The easiest way might be to put the canister's nozzle on a tube.
The project on my to-do list (please don't do this unless you know what you're doing) is to cut the top off of an expired SodaStream cylinder and fashion it into an adaptor for the hose from my 5 lb. CO2 tank. 5 lbs. of CO2 will yield something like 500 L of carbonated water, at the same $15 per fill as the SodaStream 60L refills. This should bring the cost down to $0.05 per liter or less. SodaStream will still get my money for their soda syrups, but I can disintermediate their highway-robbery CO2 service.