Store rainwater sinks / Water efficient design

This is a sink on the outside,
it is now generally sink different,
it can collect rainwater and filter out impurities,
and collect water used to wash up,
but it's not completely rely on rainwater to wash hands,
when no water in storage tank,it is the same with the normal use of the general sink, this product is mainly rainwater collected and then re-use,
efficient use of water resources.