Boiler Installation Manuals | Fault Codes & Guides

If your boiler isn’t turning on, check the power supply, fuse, and thermostat. Low pressure or a lockout due to a detected fault can also stop it working. Try resetting the boiler. If it doesn’t restart, contact a Gas Safe engineer in South West London for diagnosis.

A flashing red light usually signals a fault or system lockout. It could relate to ignition failure, low pressure, or overheating. Refer to your boiler manual for the specific code. If the light persists, book a local heating engineer to inspect the problem safely.

Boiler pressure loss often results from a water leak, bleeding radiators, or a failing expansion vessel. Check your pressure gauge — it should sit between 1 and 1.5 bar. If it drops regularly, call a heating specialist in South West London to find and fix the leak.

Locate the filling loop under your boiler and slowly open the valves until the pressure gauge reaches 1–1.5 bar. Then close the valves and reset your boiler. Always consult your model’s manual before doing this to avoid over-pressurising or damaging the system.

This could indicate a faulty diverter valve, sensor issue, or blocked plate heat exchanger. Try resetting the boiler and checking your hot water settings. If the problem continues, you’ll need a Gas Safe engineer to diagnose and replace faulty components.

A flame symbol means the burner is lit, but no heat could indicate an issue with circulation or a faulty diverter valve. Check radiators for warmth and ensure the thermostat is set correctly.

It’s recommended to service your boiler annually to ensure safe operation, efficiency, and warranty validity. Book a certified local engineer for a full inspection, flue test, and cleaning to prevent faults and breakdowns.

An EA fault means the boiler failed to ignite — often due to no gas supply, a blocked flue, or ignition failure. Check your gas supply and reset the boiler. If the issue persists, contact a Gas Safe engineer.

F22 usually indicates low water pressure or insufficient flow. Check the gauge and repressurise your system. If the code reappears after topping up, there could be a leak or faulty sensor needing professional repair.

The model number is usually printed on the boiler casing, inside the drop-down panel, or on the installation manual. You can also check the serial number sticker — often on the side or bottom of the unit.

Turn off your boiler and isolate the water supply immediately. A leak could come from a loose connection, corroded part, or faulty pressure relief valve. Do not attempt to fix it yourself — call a qualified heating engineer.

Noisy boilers often indicate trapped air, low pressure, or limescale build-up (known as kettling). Bleed radiators first. If noises continue, book a professional inspection — especially in hard water areas like South West London.

Uneven radiator heating often means trapped air or sludge in the system. Try bleeding your radiators to release air. If only certain radiators stay cold, your system might need power flushing or balancing by a heating engineer.

A low-pressure code indicates the system needs water topping up. Repressurise to around 1–1.5 bar using the filling loop. Persistent pressure loss often points to a leak or faulty expansion vessel, requiring professional attention.

Frequent shutdowns can be caused by low pressure, air in the system, thermostat issues, or a blocked flue. Check your pressure gauge and bleed radiators. If it still switches off, the boiler may be overheating or detecting a safety fault.

Most boilers have a reset button on the control panel. Hold it for 3–5 seconds until the system restarts. If the same code returns, consult the manual or call an engineer — repeated resets can mask underlying issues.

If your gauge is above 2.5 bar, the system may be overfilled. Bleed a radiator to reduce pressure. Continually high pressure might indicate a faulty expansion vessel or pressure relief valve — both require a professional fix.

Kettling occurs when limescale or sludge restricts water flow through the heat exchanger, causing boiling noises. It’s common in South West London’s hard water areas. A chemical flush or descaling treatment can fix the problem.

A weak or intermittent pilot light could result from a faulty thermocouple, gas valve issue, or draught. Don’t attempt to relight repeatedly — a Gas Safe engineer should inspect and repair it safely.

If your boiler fires up but radiators stay cold, check pressure, bleed radiators, and ensure thermostatic radiator valves are open. If still cold, the pump or diverter valve may have failed.

A lockout happens when the boiler detects a safety fault, such as ignition failure or overheating. Reset it once. If the fault code reappears, note it down and consult your manual or engineer.

E133 indicates ignition failure, usually due to no gas supply or frozen condensate pipe. Check if your gas appliances work and inspect the condensate pipe outside — thaw gently with warm water if frozen.

Cold outdoor temperatures can freeze the condensate pipe, blocking drainage and triggering a fault code. Insulate the pipe or reroute it indoors to prevent freezing during South West London winters.

Low water temperature could mean your thermostat is set too low or there’s a fault with the plate heat exchanger. Try increasing the hot water setting; if it doesn’t improve, an engineer should inspect it.

Unusual smells — like gas, burning, or metallic odours — can indicate leaks or overheating. Turn off your boiler immediately and contact an emergency gas engineer. Never ignore unusual smells.

Most boilers operate best between 1.0 and 1.5 bar when cold. Pressure will rise slightly when heating is on. If it frequently drops below or above this range, your system may have an issue.

Slow heating can result from limescale build-up, a failing thermostat, or low system pressure. A power flush or component replacement may be needed to restore efficiency.

No — even small leaks can be dangerous or cause electrical damage. Always isolate power and water, then call a Gas Safe registered engineer for professional repair.

Schedule annual servicing, bleed radiators regularly, and maintain correct pressure. Use a magnetic filter and water softener to reduce sludge and limescale build-up — especially in South West London homes.

Choose a Gas Safe registered local company with verified reviews, like WPJ Heating. We’re based in South West London and provide expert boiler repairs, servicing, and installations with fast response times and transparent pricing.