Heatrae Sadia cylinder’s expansion vessel frequently needs recharging and system pressure fluctuates widely.

Safety first: Expansion vessels are connected to pressurised hot water. Isolate and depressurise the system before working on them.

Steps to address:

• 1. Isolate and drain pressure: Close the cold inlet and open a hot tap to relieve pressure.
• 2. Check air charge: Measure the vessel’s air charge with a tyre gauge. If water comes out of the Schrader valve, the diaphragm has failed and the vessel must be replaced.
• 3. Recharge: If the diaphragm is intact, recharge to the manufacturer’s specified pressure using a pump.
• 4. Replace if necessary: Fit a new Heatrae Sadia expansion vessel of the correct size if the old one will not hold charge.