Boiler shows E11; pressure reading is excessively high and safety valve may discharge water

Safety first: Be cautious of hot water discharge from the safety valve. Allow the system to cool before relieving pressure.

Steps to check:

• Read pressure gauge: Confirm the system pressure. Values significantly above 2.5–3.0 bar indicate overpressure.
• Relieve excess pressure: Carefully bleed water from a radiator or drain point until the pressure returns to the normal cold range (around 1.0–1.5 bar).
• Check filling loop: Ensure the filling valve is fully closed and not passing water. Replace the valve if it is leaking through.
• Test expansion vessel: With the system depressurized, check the air charge on the expansion vessel using a tire gauge. Recharge to the value specified by Kospel (often around 0.8–1.0 bar) using a hand pump if low.
• Inspect vessel connection: Make sure the pipe between the system and the expansion vessel is not blocked.

When to call a technician: If the expansion vessel diaphragm is ruptured or you are unsure how to recharge it, contact a heating engineer.