Thermal Expansion Protection

Thermal expansion occurs when water is heated. For example, the water in a 40 gallon water heater that is being heated to recover after usage will expand to about 40.53 gallons when heating is complete. Because excess water cannot flow back into the city water main, this expanded water has no place to go.

When this occurs, the relief valve opens to drain hot water. This is not only a waste of water and energy, but will wear the valve down over time. Repeated thermal expansion can also cause the center flue of a gas water heater, creating a presence of hazordous carbon monoxide gas or possibly a water heater explosion.

These problems can be easily avoided by adding a small expansion tank which contains a sealed-in compressible air cushion that will compress as thermal expansion occurs. This proides adequate space to hold the additional expanded water volume rather than simply draining it.