You may do this, however, the CO2 in the sodastream tanks is FDA certified as beverage grade carbonation. Local businesses may not have this level of CO2 to refill you tank, this potentially leads to toxins being introduced into the CO2. Having the canister refilled could cause damage to the carbonator, which sodastream will not repair or replace. For the sake of our machine, it is better just to buy a new CO2 canister each time.