John Metcalfe’s San Francisco renovation included the installation of two tankless water heaters and a small circulation pump in his four-story, 3,200-sq. ft. home. The water heaters, connected in series, are located on the second floor, which is a more or less central location.
His hot-water problems should be over, right? Except they’re not.
“We now wait for up to two minutes for hot water in the kitchen and upstairs shower,” he writes in a Q&A post at GreenBuildingAdvisor.
The reasons for the long wait, and the best ways to correct this problem, are the topics for this Q&A Spotlight.
Longer waits are the norm
Traditional tank heaters keep water hot all the time, leading to what are called standby losses but also making hot water available at the turn of a tap. Not so with tankless heaters, which begin heating water only when a faucet is opened and water begins to flow.
“Different brands of tankless water heaters perform differently,” writes GBA senior editor Martin Holladay, “but in general you will have to wait a little longer for hot water from a tankless water heater than from a traditional water heater with a tank.”
Holladay notes that Metcalfe’s wait for hot water would probably be shorter if he went back to a tank-style heater. “Other ways to decrease your wait include moving the water heaters closer to the bathrooms and kitchen, and decreasing the diameter of the hot water lines,” he says.
Holladay writes that Metcalfe should make sure that his circulation pump operates by a switch located in the kitchen or bathroom. This is a less wasteful option than either a continuously operating pump or a pump on a timer. Switched pumps bring hot water to the point of use without…
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