What is likely to occur in a heating system without an expansion tank?

When a heating system lacks an expansion tank, sudden spikes in water pressure are likely to occur due to thermal expansion of the water when it heats up. As water is heated, it expands, and if there is no designated area, like an expansion tank, to accommodate this increase in volume, the pressure within the system rises significantly. This can lead to potentially damaging conditions, such as leaks, ruptured pipes, or failure of system components. The expansion tank serves to absorb this excess pressure, maintaining a stable and safe operating environment for the heating system. Therefore, without it, managing the pressure becomes a challenge, resulting in those sudden spikes as the system reacts to the changes in temperature.