Thermal expansion tanks are typically installed in conjunction with storage water heaters, but what are the requirements for tankless water heaters and thermal expansion tanks? This scenario is sometimes overlooked. Let’s look at the specifics.
Section 607.3 of the 2012 International Plumbing Code (IPC) provides the requirements for controlling pressure from thermal expansion. The requirements contained in paragraphs 607. 3 and 607.3.1 do not specifically distinguish between thermal expansion from a storage water heater, a tankless water heater, or other system equipment. Paragraph 607.3.2 does specifically require a device for controlling pressure “when there is a backflow prevention device, check valve or other device installed on the water supply system utilizing storage water heating equipment such that thermal expansion causes an increase in pressure.”
The IPC does not specifically require a thermal expansion tank or other device be installed with a tankless water heater. However, if a storage tank is used in conjunction with a tankless water heater in a closed system, which is sometimes the case with recirculation, then a means of controlling thermal expansion must be provided.