Boiler displays E10 and stops; pressure gauge may read low or zero.

Safety: Allow the system to cool before topping up. Do not over-pressurise the boiler.

• Check pressure gauge: On Alpha boilers, the cold system pressure should be around 1.0–1.5 bar. If below 1.0 bar, proceed to top up.
• Top up via filling loop: Locate the filling loop (flexible hose or built-in valves). Open the valves slowly until the gauge reaches 1.2–1.5 bar, then close both valves firmly. Reset the boiler.
• Inspect for leaks: Walk around the property and check radiators, valves, and visible pipework for signs of water. Also inspect under the boiler for drips.
• Check pressure sensor connection: A qualified person can inspect the pressure sensor on the hydraulic block, ensuring the connector is secure and free from corrosion.

If pressure drops repeatedly or E10 persists with correct pressure, contact an engineer to check for hidden leaks or a faulty pressure sensor.