Need depends on what you want to achieve.
/Frequency/ of reporting makes it easier for users to relate use to activities. Many users won't recall (or keep a record of) just when they used the pressure washer or watered the garden a month or even a week ago. And of course it also gives earlier warning of some leaks.
/Granularity/ of data allows differentiation between slow leaks and normal use (where "normal" includes e.g. people flushing loos in the night).