Baxi 720859501 Expansion Vessel 10 Litre

The Baxi 720859501 is a 10 litre expansion vessel supplied by Baxi for use in its heating appliances. Inside the vessel a diaphragm separates a pressurised air charge from the system water, so that as the water heats and expands the air cushion compresses instead of the circuit pressure climbing unchecked. It sits in the expansion vessels, tanks and cylinders group of Baxi spare parts and is intended as a direct replacement for the original unit of the same capacity.

• System pressure climbs sharply as the appliance heats up and drops back again once it cools, showing the vessel is no longer absorbing expansion.
• The pressure relief valve discharges water, or the filling loop has to be used repeatedly to bring pressure back to the correct cold reading.
• Water appears at the valve when the air charge is checked, which points to a split or perished diaphragm.
• The vessel has lost its air charge and will not hold pre-charge pressure when tested.
• Corrosion, staining or weeping is visible around the vessel body or its connection to the appliance.

• Confirm the appliance model and GC number against the compatibility information for your boiler.
• Check the physical size, mounting and connection of the existing vessel match the 10 litre replacement before fitting.
• Have a suitable gasket or sealing washer available in case the existing seal is disturbed during removal.
• Compare the part number on the existing vessel with 720859501 to be sure the correct unit is being replaced.