Heatline Expansion Vessel 3003200028

The Heatline expansion vessel is a 7 litre diaphragm vessel used in Heatline gas boilers. It absorbs the volume increase of water as the heating circuit warms, keeping system pressure within the range the boiler expects. The internal diaphragm separates the air charge from the system water, so the vessel can be recharged or replaced when the diaphragm fails.

• Boiler pressure rises sharply when the heating is running and falls again once it cools.
• System pressure drops repeatedly and needs topping up, with no visible leak on the pipework or radiators.
• Water discharges from the pressure relief valve during normal operation.
• The vessel feels heavy or sounds full of water when tapped, indicating a failed diaphragm.
• The air charge will not hold after recharging through the Schrader valve.

• Confirm the boiler model and, where applicable, the serial number against the fit list above.
• Check the vessel's physical size and connection arrangement against the unit fitted to the appliance.
• Verify the system pressure gauge and relief valve are working correctly before condemning the vessel.
• Have the system drained and the boiler isolated before removal.