Error S.22

Safety first:

- If you smell gas, evacuate occupants, do not operate the boiler or electrical switches, and call your gas emergency number immediately.

- Turn off the boiler and isolate electrical supply before removing any cover panels, unless you are only using the control panel buttons or checking visible external valves.

- If you are not confident or competent with plumbing/electrical tasks, stop and call a Gas Safe registered engineer.

Initial checks homeowners can do:

1) Note the exact code and behaviour: record S.22, whether the boiler shows any other messages, and whether you have no hot water, no central heating, or both.

2) Try a simple reset: use the boiler reset button or switch the boiler off at the mains for 1 minute and back on. See if the code clears and whether the boiler will run for DHW. If the code returns immediately, continue checks.

3) Check boiler pressure: look at the pressure gauge on the front panel. Normal pressure for a combi is usually about 1.0–1.5 bar when cold. If pressure is very low (near 0 or below 0.8 bar), the system may lock out.

4) If pressure is low, top up the system using the filling loop (only if you know how and your boiler has a filling loop): open the filling loop valves slowly while watching the pressure gauge until it reaches about 1.0–1.5 bar, then close the valves. If pressure is repeatedly low you will need an engineer.

5) Check the two isolation valves under the boiler (where the external filling loop and service valves live): make sure they are in the correct position (open where they should be) and not accidentally closed.

6) Run a hot tap and observe the boiler: listen for the pump running and observe the pressure gauge. Does the pump run but pressure/flow does not change as expected? Does the boiler try to fire then cut out with the S.22 code? Make a note of sounds (grinding, whining) which suggest a seized or failing pump.

7) Bleed radiators if you suspect trapped air in the system—air can prevent proper circulation and lead to abnormal pump signals. Re-check pressure after bleeding.

Specific diagnostic and next steps:

- If topping up pressure cleared the code and DHW now works: monitor the pressure over the next 24–48 hours. If the pressure drops again, you likely have a leak or a failing expansion vessel and need an engineer.

- If the pump does not run when a DHW demand is made (you do not hear/feel it) but the boiler is calling for hot water, the pump may be electrically dead or wiring/connector is faulty. This requires a Gas Safe engineer to test and replace the pump or repair wiring.

- If the pump runs but you see no pressure/flow change and S.22 persists, suspect a blocked/seized pump impeller, a blocked system (sludge), a defective pressure/flow sensor, or a faulty diverter valve. These faults require specialist diagnosis and component replacement/cleaning by an engineer.

- If you see other fault codes alongside S.22 (for example codes related to the pressure sensor, diverter valve, or temperature sensors), include those details when you call an engineer—they help diagnosis.

Actions to prepare for an engineer:

- Record when the fault first occurred and any events (power cuts, recent work on the system, radiator bleeding) that preceded it.

- Take a clear photo of the display showing S.22 and the pressure gauge reading.

- If you topped up pressure, note how much was required and whether the pressure held.

When to call a professional:

- Call a Gas Safe registered engineer if the S.22 code persists after simple resets and pressure checks, if the pump appears noisy, if the pump does not run when expected, if pressure repeatedly drops, or if you are not comfortable performing the safe checks listed above.

- Do not attempt internal electrical, pump or gas-valve repairs yourself. These are specialist jobs and must be carried out by a qualified engineer.

Additional notes:

- S.22 can be caused by multiple root issues; therefore if basic user-level checks do not clear it, professional diagnosis is the safe and correct next step.

- Keep the boiler isolated from use for DHW if it repeatedly locks out to avoid potential damage to the pump or other components until an engineer inspects it.