A hot water recirculation system solves the problem of waiting for hot water to travel from the water heater to the faucet. Although your hot water tank stores many gallons of heated water, some of that water sits in long lengths of unheated pipes leading to all the faucets in your home; and as it sits there unused, it cools. Typically when you first turn on a hot water faucet, you have to wait for all the cooled water in the pipes to flush down the drain before the hot water arrives. In rooms far away from your water heater, this wait can be frustratingly long. It also adds up to hundreds of gallons of water wasted every year.
Rather than running water, a hot water recirculation system delivers hot water to fixtures quickly by using a pump. The pump rapidly pulls hot water from the water heater, while simultaneously sending cooled-off water back to be filtered and reheated. This saves you energy and money at the same time!
There are two primary ways to install a hot water recirculation system: a dedicated line, or an under-the-sink retrofit. Dedicated lines are typically used in new construction and they consist of a pipe line built into the house's plumbing system. Their sole job is to return water back from the regular pipes to a filter and the hot water heater for reheating. An under-the-sink retrofit is usually chosen when a homeowner adds a hot water recirculation system to an older home. It's a system of pipes installed beneath a sink's drain.
The hot water recirculation system itself is generally made up of a pump, a filter, an integrated electronic controller and a zone valve. It's activated by a button, thermostat, timer or motion sensor, or runs continuously.
When the system is activated, the pump speeds the flow of hot water to the tap while simultaneously beginning to recirculate cooler water in the line by sending it back to the water heater through the cold water pipe. Once the water in the recirculating pipe has reached the desired temperature, a control closes the zone valve and turns off the pump. So, instead of gallons of water wasted down the drain, this system returns that cool water back to the water heater, while providing hot water immediately at every faucet.
Although hotels – and other buildings where hot water demand is high – often use a continuous system, it's a good idea for a homeowner to use some type of timer on a hot water recirculation system, in order to save money. Otherwise the pump will be on continuously, which will also place a high demand on your water heater.
As you can see, hot water recirculation systems can be a great addition to your plumbing, so much so that some cities have ordered all new homes to be constructed with them. It's important to check with your local plumbing contractor before installing one in an older home, since some municipalities require that this work be performed only by licensed plumbing contractors.
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