How much water does my pump need to pump?

This mainly depends on how many brewing groups your espresso machine has. There 3 types of pumps, a 50, 100 and a 200 L/H pump. For a single group and a smaller 2 group espresso machine you can work with a 50 or a 100 L pump. When you have more then 2 brewing groups you do need to go for a 180-200 L/H pump. Price wise there is no difference between these pump versions.