In this report
Overview
How to choose
What you'll pay
How they work
October 2008
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How they work
Tankless models don’t store hot water. When hot water is needed, water flows through the device and the flow sensor fires the burner. Water lines around the heat exchanger warm the water to the desired temperature. When the hot-water valve is closed, the flow sensor turns off the burner. (The flow must be fast enough, typically a half-gallon per minute, to turn on the sensor.) Capacity is expressed in gallons per minute.

Illustration of how a tankless water heater works
Illustration by Jim Kopp


1
Exhaust

2
Heat exchanger

3
Burner

4
Fan

5
Control panel

6
Flow sensor

7
Hot water to faucet

8
Gas supply

9
Cold water
coming in

10
Cold water
to faucet








Posted: September 2008 — Consumer Reports Magazine issue: October 2008