As water in a hot water system expands, what happens to the pressure?

In a hot water system, as water is heated, it expands due to the increase in temperature. In a closed system where the water cannot escape, this expansion leads to an increase in pressure. However, many hot water systems are designed with pressure regulators or expansion tanks that can accommodate this increased pressure.

In such systems, the expansion tank absorbs the extra water and allows for the pressure to remain relatively constant despite the thermal expansion of the water. This is crucial for maintaining the integrity of the system and preventing damage due to excessive pressure.

If the system was not designed with these features, increased pressure could lead to dangerous situations, making it essential for systems to be engineered to manage this change effectively. Thus, in general circumstances involving proper hot water system design, the pressure can be kept stable even as the water expands.