Recirculating hot water for greater efficiency
You turn the faucet, and the shower head comes to life. You stand in the bathroom testing the water every few seconds until it's ready. This process isn't very efficient—for every minute that goes by, the shower is using approximately two gallons of water.
It's not just the shower. There are probably four or five times a day that you turn the hot water tap at the sink and wait for the water to run hot. Recirculating hot water is a method to make water hot right when you need it, which can save you time and conserve your water usage.
How they work
Before we talk about the environmental benefits, let’s talk about plumbing. Water runs through your house in pipes, powered by electric pumps. A tank in your house heats water, either by gas or electricity (rather like a pot of water on a stovetop), and pipes it all the way to your shower.
A hot water recirculation pump.
When you turn the shower off, water sits in these pipes and becomes cold. Then, the next time you turn the shower on, all of that cold water pumps out before the hot water appears.
Circulating hot water solves this problem by keeping the water moving. Water in pipes only flows one way, so the recirculating hot water pumps the water back to the hot water heater.
What they cost
There is a trade-off in recirculating hot water. Because the pump uses electricity that you otherwise would not be using, new recirculating hot water pumps have timers that only run during typical hot water use times of the day.
These pumps run about $200, and if you’re handy, you can install it yourself. It's possible to save up to 10,000 gallons of water per year, depending on the size of your household and your water use.