Error E1

Safety first

- If you smell gas: turn off the gas supply at the meter, leave the property immediately, do not operate electrical switches, and call the emergency gas number. Do not attempt any repairs.

- Turn the boiler off at the programmer and isolate electrical power at the fused spur before opening panels or working near live parts. Do not remove the boiler casing — internal work must be done by a Gas Safe engineer.

- When repressurising, work on a cold system where possible and take care to avoid spills; keep children and pets away.

Initial quick checks you can do

1. Note the exact display message and any flashing lights; check the boiler manual for your model’s description of E1/E119/E110 etc.

2. Look at the pressure gauge on the boiler. Normal cold system pressure is usually around 1.0–1.5 bar. If it’s below about 0.5 bar the boiler will often lock out.

3. Check for obvious leaks under the boiler, around radiators, radiator valves, and visible pipework. A wet patch or dripping indicates a leak that needs repair.

4. Check the condensate pipe if it’s outside and it’s freezing weather — a frozen condensate can also cause faults and shutdowns.

5. Check room thermostat and programmer (batteries if wireless) to ensure the boiler is being called to fire.

Step-by-step diagnostic and fix (DIY safe tasks)

1. Turn off the heating via the programmer and switch the boiler to off/cold. Allow it to sit a few minutes.

2. Repressurise the system using the boiler filling loop: locate the flexible filling loop under the boiler (silver/flexible pipe with one or two small valves). Confirm the loop is fitted correctly and valves are currently closed.

3. Open one valve then the other slowly and watch the pressure gauge. Stop when the gauge reaches around 1.2–1.5 bar (check your boiler manual for the exact recommended pressure). Close both valves fully and return them to their original closed position. Some boilers require the filling loop to be removed after topping up — follow your manual.

4. Switch the boiler back on and reset the fault using the boiler reset button if required. Refer to your manual for reset procedure. One reset after correct pressure is fine; do not continually reset a repeating fault.

5. Run the heating and bleed radiators to remove trapped air (this can improve circulation and stop local overheating). Start with the radiators at the highest point in the house and work downwards. Use a radiator key or screwdriver, have a container to catch water, and close the bleed valve when only water (no air) comes out. Recheck and top up system pressure afterwards because bleeding can lower pressure.

6. After repressurising and bleeding, monitor the pressure gauge over the next 24 hours. If pressure remains stable and the E1 fault clears, the immediate issue is solved.

If the problem persists or further diagnostics are needed

- If pressure keeps dropping: there is likely a leak in the system, a faulty pressure relief valve, or a failing expansion vessel. Look again for signs of leaks (radiators, valves, boiler, pipework), then call a Gas Safe engineer.

- If you cannot find or operate the filling loop or the boiler will not accept pressure, do not force valves. Stop and call a Gas Safe engineer.

- If the boiler shows overheating symptoms (very hot surfaces, unusual noises, rapid cycling) or will not reset, switch it off and call a professional.

- Frozen condensate pipe: thaw with warm (not boiling) water; if you’re unsure call an engineer.

- Electrical or gas supply faults, repeated lockouts, or internal component failures (expansion vessel, pressure sensor, pump, heat exchanger) require a qualified Gas Safe registered heating engineer.

When to call a professional

- Any visible water leak or persistent loss of pressure.

- Boiler will not restart after repressurising and reset.

- You smell gas, see corrosion, or discover damaged pipework.

- You are uncomfortable performing any of the steps above.

A Gas Safe registered heating engineer should be used for repairs involving gas connections, replacing internal parts, diagnosing expansion vessel or pressure relief valve faults, and any work that requires opening the boiler casing.