Grant Expansion Vessel MPSS01

The Grant 12 litre expansion vessel is a sealed diaphragm vessel used to absorb the expansion of water as it heats within a sealed heating system. It is fitted to Grant oil-fired combi and Euroflame boiler ranges, where it maintains system pressure and protects components from excessive pressure rise. The vessel carries part number MPSS01.

• System pressure rises sharply once the boiler fires and falls again when it cools
• The pressure relief valve discharges water during heating cycles
• Frequent topping up of system pressure is needed to keep the boiler running
• Water is heard sloshing inside the vessel when it is tapped, indicating a failed diaphragm
• The vessel is corroded, weeping at the seam, or has lost its pre-charge

• Confirm the existing vessel is rated at 12 litres before ordering
• Check the appliance model against the fit list above, as several Grant ranges are covered
• Inspect the pressure relief valve and system pressure gauge at the same time, as these are often affected by the same fault
• Verify the system has been depressurised and drained before removal of the old vessel