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Don’t get lost in all the water heater terms. Learn how to speak “hot water” using this glossary so you can make smarter choices.

Basic Water Heater Terms

Limited Warranty

Commercial water heaters come with varying levels of coverage. A water heater can have a ‘Limited Warranty’ for anywhere from five to twelve years. In some cases, coverage includes replacement of tank and parts at no charge when involving the following:

  • Tank Leaks
  • Malfunctioning Component Parts
  • Failure Due to Manufacturer Defects

Check the warranty (included with your water heater) or contact the manufacturer for details on your commercial water heaters specific warranty coverage.

Rated Storage Volume

The Rated Storage Volume is the water storage capacity of a water heater, in gallons, as specified by the manufacturer.


Input is the amount of gas or electricity used per hour to heat the water in the tank. Gas water heaters measure Input using BTUs (British Thermal Unit). Electric water heaters measure it in Watts. A higher Input means that the water heater can heat more water, faster when necessary.

Recovery (at 90º Temperature Rise)

Recovery converts BTU or Watt input into gallons heater per one hour (GPH). For example, a 40,000 BTU gas water heater recovers, or heats, 41 gallons in one hour. 90° Rise means that the water temperature increased by 90°F.

First Hour Output

First Hour Output (also called First Hour Rating) is the ‘peak demand’ figure that estimates how much water the water heater will deliver during the first hour of use. It combines the heater’s storage capacity with its recovery capability during one hour of operation.

Now that you know how to speak water heater, you can make more informed decisions about your water heater replacement.

If you still aren’t sure what’s the right commercial water heater for your business, call Wallingford Sales today. We can help you choose the right one for you. See our online catalog today or contact us at 866.977.2537.

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