| 摘要 |
Disclosed is a heater including a back-flow preventing device located at or adjacent an outlet of the heater. In some embodiments, the back-flow preventing device has an open position and a closed position. When the back-flow preventing device is in the open position, water is able to flow freely through the heater. When back-flow preventing device is in the closed position, water is prevented from flowing or migrating back into the heater.
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