What is a Hot Water Recirculation Pump?
The recirculation or booster pump is a device that quickly draws hot water from your tank type water heater and replaces the cooled off hot water in your hot water pipes with hot water by sending the cooled off "hot" water back to the water heater via the cold water line where it is heated back up.
Think of it this way, when you usually let the cooled off hot water water run down the drain until it gets hot again, the cooled off water in your hot water pipes has now been replaced with hot water. With the recirculation pump, the cooled off hot water is just sent back to the water heater (through the cold water line) and very quickly replaced with hot water instead of being dumped down the drain.
The result is hot water with very little wait time, around 60% to 80% faster than standard water heater configurations.