Expansion tanks

Products

Zilio

An expansion tank is a crucial technical component used in closed-loop heating systems to balance the excess pressure caused by the thermal expansion of water. When water heats up, it expands, leading to increased pressure within the system. If this pressure is not controlled, it can damage the boiler, pipes, and other components of the heating system. Expansion tanks are installed to prevent such risks.

Modern expansion tanks are equipped with an internal flexible diaphragm (membrane). This diaphragm divides the tank into two chambers – one for water and the other for air or nitrogen gas. As water expands, the membrane compresses, absorbing the extra volume and keeping the system pressure stable. This structure is known as a diaphragm expansion tank, and it is now the standard and only reliable type used in modern systems.
Non-diaphragm expansion tanks are no longer used in contemporary heating systems because in those types, air and water are in direct contact, which can lead to corrosion, pressure drops, and the need for frequent maintenance.

Expansion tanks are generally classified into two types according to their installation style: vertical and horizontal models.

  • Vertical expansion tanks are typically used in boiler rooms or floor-mounted systems. These tanks are placed on the ground and can be easily adapted to most central heating systems. Vertical placement saves space and provides practical and aesthetic benefits.

  • Horizontal expansion tanks, on the other hand, are mostly used in wall-mounted combi boilers and compact systems. These tanks are integrated into or mounted above boilers, offering a space-saving and visually neat design. In many cases, horizontal tanks are supported by special brackets fixed to the boiler housing.

The volume of the expansion tank must be chosen according to the size of the heating system. Common models include 6-liter, 8-liter, 12-liter, 24-liter, and 35-liter tanks. While smaller tanks (6–12L) are sufficient for apartments and private homes, larger tanks (24L and above) are required for large houses and central heating rooms.

These tanks are effectively used in systems with circulation pumps, as well as in classic radiator heating systems. Additionally, they are found in solar heating systems and domestic hot water circuits.

In summary, the expansion tank is an essential element in any heating system. It maintains pressure stability, protects the boiler and piping, and ensures the safety and long-term functionality of the system. Proper selection and installation of an expansion tank are crucial for both user comfort and energy efficiency.