It depends on the system water volume, temperature range and pressure settings. Use the manufacturer’s sizing guidance or ask an installer.
Sealed-System Pressure Control and Vessel Capacity
System pressure rises as water heats. An expansion vessel provides space for that increase, helping a sealed heating circuit operate within its specified pressure range. MacBlair stocks Sanbra heating vessels in capacities from 12 to 50 litres on the visible page, alongside 8, 18, 24 and 35 litre vessel-and-kit options.
The category also includes Altecnic and Sanbra potable-water expansion vessels. Heating and drinking-water duties are not interchangeable: check the vessel marking, pre-charge, connection and required volume against the installation. A replacement for a system boiler should be sized for the entire circuit, not chosen solely by the capacity of the old vessel.
An installer should investigate repeated pressure loss before replacing a vessel; a leak or faulty valve may be responsible. When renewing pipework, check the compatible pipe fittings and allow access for future testing. The wider plumbing and heating range includes the other components needed around a sealed system.
Expansion Vessel FAQ's
Do not assume so. Heating and potable-water vessels have different approvals and specifications; choose one marked for the intended duty.
A lost pre-charge or failed vessel diaphragm is one possible cause. A heating engineer should check the vessel and other components.
It is a listed vessel with associated connection components. Check the contents and compatibility against the proposed installation.
Not automatically. Confirm the system volume and design pressure, especially if radiators or pipework have changed.