CSLB C-36 Plumbing ContractorPlanning and EstimatingMedium
A plumbing contractor is preparing to install a new water heater in a commercial property. The design specifications require that the water heater be equipped with a tempering tank. What is the primary purpose of installing a tempering tank in conjunction with a commercial water heater?
- ATo pre-heat incoming cold water using waste heat.
- BTo reduce the operating pressure within the hot water system.
- CTo prevent thermal expansion within the water heater tank.
- DTo increase the water heater's overall BTU output.
Show answer & explanationAnswer & explanation
Correct answer: A. To pre-heat incoming cold water using waste heat.
A tempering tank, also known as a pre-heat tank or an energy recovery tank, is primarily used to capture waste heat from sources like drain water or flue gases to pre-heat incoming cold water before it enters the main water heater. This reduces the energy required by the primary water heater.
Why the other options are wrong
- B. Pressure reduction is typically handled by a pressure-reducing valve, not a tempering tank.
- C. Thermal expansion is managed by an expansion tank, not a tempering tank.
- D. Tempering tanks do not directly increase BTU output; they improve efficiency by pre-heating.
Tempering Tank (Plumbing)
A tank designed to pre-heat incoming cold water, typically using a secondary heat source such as drain water heat recovery or flue gas heat, before it enters the main water heater, thereby increasing energy efficiency.
- Improves energy efficiency of the hot water system.
- Reduces the load on the primary water heater.
- Often used in commercial or high-demand residential applications.
Memory trick: Tempering tank: 'T' for 'Take' waste heat, 'T' for 'Turn' cold water warm.