How can this little Pump save 50 000 liter water a year for the houshold

This little circular pump is inline with the Hot water line at the hot water Tank. A special thermal Bypass comfort Valve installed under the sink furthers away from the Tank allows water to flow from the hot line in to the cold line till the hot water reaches the Valvue. 

Saving 1000's of liter of water going town the drain

never wait for Hot water again.