Recirculating pumps are usually used to circulate hot water in homes so that the faucet will provide hot water instantly when the user turns the faucet on. In areas where water conservation issues are becoming increasingly important and with rapidly expanding and urbanizing populations, local water authorities offer rebates to homeowners and builders who install a circulating pump to save on water consumption.
In typical one-way plumbing that doesn’t have a circulation pump, water is piped directly from the water heater through the pipes to the tap. When the tap is shut off, the remaining water stays in the pipes and cools over time. This is the reason you have to wait for the water to “warm up” when you turn the tap on the next time you take a shower.
When you add a circulation pump, the water is constantly being circulated through the water heater. The result is that the water in the pipes always stays hot, and you aren’t wasting water waiting for the hot water to push the remaining cold water out of the pipe.
The tradeoff for using a circulator pump is the energy which it takes to operate the pump and the additional demand on the water heater to make up for the heat lost from keeping the water in the pipes hot. The energy use can be significantly reduced by using a circulating pump that has a thermostat. This allows the owner to set the desired temperature of water to be maintained in the pipes.