Chaffoteaux 106 Fault Code: Causes, Fixes & Repair Costs
What does the Chaffoteaux 106 fault code mean?
Fault code 106 on Chaffoteaux boilers signals that the boiler has been unable to confirm adequate water flow through the primary heating circuit. When this check fails, the boiler locks out as a protective measure to prevent overheating and component damage. You may see the code displayed as '1 06' on the control panel, depending on the model. The boiler is essentially saying: 'I tried to circulate water, but I could not verify enough movement to operate safely.' This fault appears across several Chaffoteaux models including the Talia, Alixia, and Expert Control ranges. Note that older Britony models used LED blink codes rather than numeric displays, so always cross-reference with your specific model's manual.
General guidance only — not a substitute for professional advice, and not certified by a Gas Safe engineer. Always have your specific appliance assessed by a qualified professional. Any gas work must be carried out by a Gas Safe registered engineer. If you smell gas or suspect carbon monoxide, leave the property and call the National Gas Emergency line on 0800 111 999.
Common causes
- Low system pressure Common
If the system pressure has dropped below roughly 0.5–1.0 bar, the boiler's internal pressure sensor will prevent normal operation, meaning the pump never gets a proper chance to circulate water. This is a very frequent cause of code 106 and is something a homeowner can address by topping up via the filling loop.
- Seized or faulty circulation pump Common
A stuck or seized pump impeller is a very common culprit, particularly if the boiler has been dormant for a long period — for example, over summer. Sludge or simple inactivity can cause the pump internals to seize, so although the boiler commands the pump to run, water movement is negligible or absent.
- Sludge or magnetite build-up restricting flow Common
Over time, corrosion by-products — primarily magnetite — accumulate in the narrowest parts of the heating circuit, including the pump and heat exchanger ports. Even a partially blocked circuit can reduce flow enough to trigger a 106 lockout. A system without adequate corrosion inhibitor is especially vulnerable.
- Faulty or failing flow sensor Sometimes
The flow sensor monitors water movement and reports back to the boiler's control board. If it gives an incorrect reading — either because it has failed outright or because its ports are partially blocked with debris — the boiler will conclude there is insufficient flow and lock out, even if the pump is actually running.
- Blocked primary heat exchanger Sometimes
A severely scaled or sludge-blocked heat exchanger creates genuine flow restriction. In this scenario the pump is working, but it simply cannot push water through the blockage at an adequate rate. This is more common in hard-water areas and in older systems that have never been power-flushed.
- Water leak causing recurring pressure loss Sometimes
A slow leak anywhere in the system — from radiator valves, pipe joints, the pressure relief valve, or boiler seals — causes pressure to drop repeatedly. If you find yourself topping up the pressure regularly and code 106 keeps returning, a leak is the most likely reason.
How to fix it
- Reset the boiler DIY safe
Press the reset button on the boiler's control panel and allow the boiler to attempt a restart. A single reset is a reasonable first step. If the boiler fires up and then locks out again after 5–10 minutes, note this pattern — it can suggest a component that behaves differently once it warms up, such as a flow sensor that drifts with temperature. Limit yourself to two or three reset attempts; repeated resets without identifying the cause can mask an underlying problem.
- Check the system pressure gauge DIY safe
Look at the pressure gauge, typically located on the front panel or beneath the boiler. A cold system should read between 1.0 and 1.5 bar. If it reads below 1.0 bar, low pressure is very likely contributing to the fault and should be addressed before anything else.
- Top up system pressure using the filling loop DIY safe
Locate the filling loop — usually a short, braided silver hose with one or two small valves, found beneath the boiler. Slowly open the valve(s) and watch the pressure gauge rise. Close the valve(s) once the needle reaches approximately 1.2–1.5 bar. Do not overfill; pressure above 2.5–3.0 bar can cause the pressure relief valve to discharge. Once topped up, try resetting the boiler again.
- Inspect for visible leaks DIY safe
If the pressure was low, or if it drops again shortly after topping up, look around the boiler, radiators, and any visible pipework for damp patches, rust staining, or white limescale deposits — all signs of a slow leak. Do not re-pressurise repeatedly without finding and fixing the source; this dilutes the system inhibitor and can worsen corrosion over time.
- Check that all system valves are fully open DIY safe
Make sure the lockshield and thermostatic valves on all radiators are open and have not been accidentally closed. Also confirm that any isolating valves near the boiler — on the flow and return pipes — are in the fully open position. Restricted flow from a closed valve can trigger a 106 lockout.
- Call a Gas Safe registered engineer if the fault persists Gas Safe engineer
If code 106 returns after you have checked the pressure, reset the boiler, and confirmed valves are open, the cause is likely a component fault that requires professional diagnosis. A Gas Safe engineer will inspect and test the circulation pump (and free or replace it if seized), check the flow sensor for failure or blockage, assess the heat exchanger for scale or sludge restriction, and advise on a power flush if magnetite build-up is found. Do not attempt to work on the pump, flow sensor, heat exchanger, or any internal boiler components yourself.
Parts you may need
- Circulation pump · from £80
- Flow sensor / flow switch · from £25
- Pressure sensor · from £20
- System inhibitor (e.g. Fernox F1 or Sentinel X100) · from £15
- Magnetic system filter (e.g. Magnaclean) · from £55
The exact spare depends on your boiler's GC number (on the data badge). Check this against the part before buying.
Typical repair cost
Expect to pay roughly £120–£350, depending on the underlying cause.
Frequently asked questions
Can I fix Chaffoteaux fault code 106 myself?
Some of the initial checks are perfectly safe for a homeowner — topping up system pressure via the filling loop, resetting the boiler, and checking that radiator valves are open. However, if those steps do not clear the fault, the likely causes (a seized pump, faulty flow sensor, or blocked heat exchanger) require a Gas Safe registered engineer. Working on internal boiler components without the correct qualifications is both dangerous and illegal in the UK.
Why does code 106 keep coming back after I reset the boiler?
A fault that clears on reset but returns within minutes or hours usually points to either a recurring pressure drop (which suggests a leak somewhere in the system) or a component that is on its way to failure — commonly the circulation pump or flow sensor. A one-off lockout that stays cleared after a reset and pressure top-up is less concerning, but a pattern of returns needs a Gas Safe engineer to investigate properly.
How much does it cost to repair a Chaffoteaux 106 fault in the UK?
For the most common repairs — freeing or replacing a seized circulation pump, or replacing a flow sensor — most homeowners pay somewhere in the region of £120 to £350 including parts and labour. A pump replacement alone typically averages around £200–£250 all-in. If the fault is traced to a heavily scaled or sludge-blocked heat exchanger requiring replacement, costs can rise to £400–£600 or more, and at that level a full boiler replacement may be worth considering. A power flush, if the system has significant sludge, usually costs £300–£500 depending on the number of radiators.
How can I prevent Chaffoteaux fault code 106 from recurring?
Annual servicing by a Gas Safe engineer is the single most effective measure. During a service the engineer will check pump operation, inhibitor concentration, and system pressure — all factors directly linked to this fault. Adding a magnetic filter (such as a Magnaclean or similar) to the return pipe captures magnetite before it can block the pump or heat exchanger. Topping up corrosion inhibitor every year or two, and ensuring the system pressure stays between 1.0 and 1.5 bar, will also significantly reduce the risk of a 106 lockout.