Andrews Expansion Vessel G099

The Andrews G099 is a 35 litre expansion vessel rated at 3.5 bar, fitted to Andrews water heaters to absorb the expansion of water as it is heated in a sealed system. It holds the air charge that cushions this expansion, keeping system pressure within safe limits and reducing stress on the heater and its components.

• Water discharging from the pressure relief valve as the heater warms up
• System pressure climbing sharply during heat-up and dropping again once the heater cools
• The vessel feels heavy or sounds full of water when tapped, indicating the air charge has been lost
• Pressure gauge readings that will not settle or hold steady
• Corrosion, staining or weeping around the vessel connection

• Confirm the existing vessel's capacity and pressure rating match 35 litres and 3.5 bar
• Check your Andrews water heater model against the manufacturer's parts list
• Check the installation space and the connection arrangement before removing the old vessel
• Depressurise and drain the system before fitting