Boiler shows E10, system pressure gauge low, boiler will not fire

Safety first: Allow the system to cool before topping up pressure to avoid scalding.

User checks:

• Check the pressure gauge on the boiler; if below 1.0 bar, top up using the filling loop until 1.0–1.5 bar when cold.
• Reset the boiler after topping up and check for normal operation.
• Walk around the property and look for visible leaks on radiators, valves, and pipework.

Engineer checks:

• Inspect the boiler and system for hidden leaks, including underfloor pipework and around the pressure relief valve discharge pipe.
• Test the pressure sensor or pressure switch for correct operation and replace if faulty.
• Check the filling loop for slow filling or backflow issues; replace if defective.

If pressure repeatedly drops, a leak or expansion vessel issue is likely and should be investigated by a heating engineer.