Saunier Duval Expansion Vessel 8 Litre 0020018451

The expansion vessel is an 8 litre diaphragm vessel manufactured by Saunier Duval, supplied with an O-ring. It is fitted to Thema Condens and Themaplus Condens gas boilers, where it absorbs the volume increase of the sealed heating system as the water heats and expands. This keeps system pressure stable and protects components such as the pressure relief valve from repeated discharge.

• Boiler pressure rises sharply when the heating is running and falls again once it cools.
• System pressure is repeatedly lost and requires frequent topping up.
• Water discharges from the pressure relief valve during normal heating cycles.
• Water or air is found at the vessel's air valve when the charge is checked.
• Visible corrosion, distortion or water staining on the vessel body.

• Confirm your boiler model against the fitment list above.
• Check that the existing vessel is rated at 8 litre.
• Inspect the vessel connection and sealing face before fitting the new O-ring.
• Verify system pressure and expansion vessel charge once the part is installed.