Thanks for explaining that. I still have some possible concerns that the pump would need to be active a lot more than that for us - we'd easily go through a few litres of soda water a day and with people visiting I wouldn't be surprised if we went through 10L at the height of summer.The pumps (rotary vane) are the same as those used in commercial coffee machines. Some can do both 50/60Hz, ones that are not won't be impacted too much in a domestic situation as they would barely run much more than once a day for a few seconds a time.