True or False: The primary function of an expansion tank is to absorb air or pressure from the plumbing system.

The primary function of an expansion tank is indeed to absorb air or pressure from the plumbing system, making the answer true. Expansion tanks are designed to accommodate the expansion of water as it heats up in heating systems or when water pressure fluctuates within plumbing systems. When the water is heated, it expands, and without a mechanism to absorb this increase in volume, pressure could build up to unsafe levels, potentially damaging pipes, fixtures, or appliances. The expansion tank provides a space for this expanded water to flow into, thereby regulating the system's pressure and protecting the plumbing infrastructure.

The alternative choices address functions not applicable to expansion tanks. For instance, increasing water temperature and storing excess water are not primary roles of expansion tanks. Their main purpose revolves around managing pressure and mitigating the effects of thermal expansion in plumbing systems.