Worcester Bosch 1022 Fault Code: Causes, Fixes & Repair Costs
What does the Worcester Bosch 1022 fault code mean?
Fault code 1022 appears on certain Worcester Bosch Greenstar boilers — particularly older CDi and conventional Greenstar models that use a numeric fault code display rather than the newer alphanumeric system. When the boiler detects that the heating circuit pump is not circulating water correctly, it locks out and displays 1022. The boiler is essentially telling you that it cannot confirm proper water movement around the system: the pump may be seized, air-locked, or failing electrically. In some cases — especially on CDi Conventionals — it can also flag on initial installation or if the flow temperature rises unusually fast, pointing to a wider circulation problem rather than a purely mechanical pump failure. Until the root cause is resolved, the boiler will remain locked out to prevent overheating damage to the heat exchanger.
General guidance only — not a substitute for professional advice. 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
- Seized or stuck pump Common
Over time — particularly in systems that sit idle during summer — the pump impeller can seize solid. The boiler fires, detects no circulation, and locks out with 1022. A Gas Safe engineer can sometimes free a mildly seized pump by releasing the bleed screw on the pump head; a fully failed pump will need replacing.
- Airlock in the heating circuit Common
Trapped air can prevent the pump from moving water effectively even if the pump itself is fine. This is more likely after recent radiator work, a system drain-down, or if system pressure has been very low for some time. Bleeding radiators and checking pressure can help, but an engineer will confirm whether a persistent airlock remains.
- Sludge or debris blockage Common
Magnetite sludge and scale build-up — common in older systems without a magnetic filter — can restrict flow to the point where the pump cannot maintain adequate circulation. The boiler then interprets this as a pump fault. A powerflush is typically required to resolve it.
- Electrical or wiring fault to the pump Sometimes
A wiring fault, corroded connection, or failed relay can stop the pump receiving the correct signal or power, causing it to appear blocked even when the mechanical parts are intact. Diagnosis requires an engineer with the correct test equipment.
- Flow temperature rising too quickly Sometimes
If the heating system is undersized, heavily restricted, or the pump speed is set too low, the water temperature can spike faster than expected — mimicking a circulation fault and triggering 1022. This is sometimes seen on new installations that have not been commissioned correctly.
- Faulty pump or PCB sending incorrect readings Rare
A failing pump motor drawing abnormal current, or a PCB that is misreading pump feedback signals, can cause spurious 1022 lockouts even when circulation is adequate. Both components would need testing by an engineer.
How to fix it
- Note the fault code and attempt a single boiler reset DIY safe
Before calling anyone, write down the fault code and any other information on the display. Locate your boiler's reset button (usually marked with a flame symbol or labelled 'Reset') and hold it for the time specified in your user guide — typically 3–5 seconds. If the boiler fires and runs normally, monitor it over the next hour. If 1022 returns immediately or after a short time, do not keep resetting — move on to the checks below and then call an engineer.
- Check system pressure at the gauge DIY safe
Look at the pressure gauge on the boiler front panel. A healthy reading is between 1 and 1.5 bar when the system is cold. If it reads below 0.8 bar, low pressure may be contributing to poor circulation. Top up using the filling loop (usually a flexible braided hose with one or two valves beneath the boiler) until the gauge reads around 1.2 bar, then close the filling loop valves. If pressure drops again quickly, there may be a leak — call an engineer.
- Bleed the radiators to release trapped air DIY safe
Switch the heating off and allow the system to cool. Starting from the ground floor, use a radiator bleed key to open each bleed valve a half-turn until water — not air — trickles out, then close it. Re-check the boiler pressure afterwards and top up if it has dropped below 1 bar. After bleeding, attempt another reset. If 1022 returns, the airlock has either not cleared or the issue lies elsewhere.
- Check that your gas supply is working DIY safe
Check that other gas appliances in your home (hob, gas fire) are working normally. If they are not, your gas supply may be interrupted — contact your gas network provider (0800 111 999 in the UK) immediately. If other appliances work fine, the gas supply to the boiler is not the primary issue here.
- Call a Gas Safe registered engineer to inspect the pump Gas Safe engineer
If the fault persists after the checks above, the pump or related components need hands-on inspection. An engineer will test pump operation, check electrical continuity to the pump, and assess whether the impeller is seized. They can attempt to free a stuck pump, replace a failed one, or investigate wiring faults. Do not attempt to open or work on the pump yourself — it is part of the sealed heating circuit and working on it incorrectly can cause leaks or further damage.
- Engineer to assess for sludge and carry out a powerflush if required Gas Safe engineer
If circulation remains poor after a pump repair or replacement, the engineer may recommend a powerflush. This process pushes a high-velocity flow of water and cleaning chemicals through the system to remove magnetite sludge and limescale. A magnetic filter should then be fitted to prevent recurrence. Powerflushing is a skilled job and must be carried out by a qualified engineer.
- Engineer to inspect PCB and wiring harness if pump tests normal Gas Safe engineer
If the pump is mechanically and electrically sound but 1022 persists, the fault may lie with the PCB or the wiring between it and the pump. The engineer will carry out further electrical tests to isolate the fault. PCB replacement or wiring repairs must only be performed by a Gas Safe registered engineer.
Parts you may need
- Central heating circulator pump (e.g. Grundfos UPS2 or Wilo equivalent) · from £85
- Pump wiring harness / pump connector loom · from £25
- Magnetic system filter (e.g. Adey MagnaClean Pro2) · from £65
- Boiler PCB (main printed circuit board) · from £195
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 £150–£380, depending on the underlying cause.
Frequently asked questions
Can I fix Worcester Bosch fault code 1022 myself?
The initial checks — topping up system pressure, bleeding radiators, and a single reset — are safe for a homeowner to carry out. However, the underlying cause of 1022 almost always requires a Gas Safe registered engineer. Working on the pump, wiring, or any internal boiler component yourself is not safe, may void your warranty, and could invalidate your home insurance. If the simple checks above do not clear the fault, book an engineer.
How much does it cost to fix a 1022 fault on a Worcester Bosch boiler?
For most households, the repair comes to between £150 and £380 all in — covering the engineer's time and a replacement pump if needed. If sludge is the root cause, a powerflush adds roughly £300–£500 on top. In rare cases where the PCB is at fault, costs can climb higher; mention this to your engineer if the pump tests fine. Emergency call-outs in evenings or at weekends typically carry a £100–£200 premium over standard rates.
Why does my Worcester Bosch keep showing 1022 after I reset it?
If 1022 returns immediately or within a short time after every reset, there is an active underlying fault — most likely a seized pump, persistent airlock, or wiring issue — that the reset cannot fix. Repeatedly resetting a boiler in this state can mask the problem and risk damaging components further. Limit resets to two or three attempts and then call a Gas Safe engineer to diagnose the root cause properly.
My boiler is a Worcester Bosch CDi Conventional and showed 1022 right after installation — is that normal?
A 1022 fault on a newly installed CDi Conventional is not uncommon and is usually down to commissioning issues: trapped air, incorrect pump speed settings, or a flow temperature rising too quickly on first fire-up. The installing engineer should return to re-commission the boiler, bleed the system thoroughly, and confirm the pump is set to the correct speed for your system. It should not be left as a recurring fault.