Potterton E193 Fault Code: Causes, Fixes & Repair Costs
What does the Potterton E193 fault code mean?
The E193 code on a Potterton boiler signals a circulation problem — the boiler has detected that hot water is not moving around the heating system as it should. This is most commonly linked to a pump or flow fault, where the boiler senses a cold return pipe or inadequate water movement. On some Potterton models the code can also point to a communication breakdown between the control board and the room thermostat, though the circulation interpretation is the more widely reported cause. Either way, the boiler will typically lock out to protect itself, and you may notice cold radiators, gurgling noises from the pipework, or unusual sounds from the pump area.
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
- Faulty or seized circulation pump Common
The pump is responsible for pushing hot water around your radiators and back to the boiler. If it has seized, developed a blown seal, or its impeller is jammed with debris, water flow drops off sharply and the boiler detects a cold return — triggering E193. A seized pump is often the single most common reason for this code appearing.
- Sludge or debris blockage in the system Common
Over time, corroded pipework and radiators shed magnetite sludge and limescale deposits. These can accumulate in the pump housing, heat exchanger, or pipework bends, restricting circulation enough to trigger a flow fault. Older systems without a magnetic filter are particularly vulnerable.
- Airlocks in the heating circuit Sometimes
Pockets of trapped air can prevent water from circulating properly, causing uneven heating and confusing the boiler's flow sensors. Bleeding radiators can release minor airlocks, but persistent or deep-seated airlocks may need professional attention.
- Low system pressure Sometimes
If the boiler's pressure has dropped below roughly 1 bar, there may not be enough water volume in the system to sustain adequate circulation. The boiler may interpret this as a flow fault and display E193. Check the pressure gauge on the front of the boiler.
- Control board to thermostat communication failure Rare
On certain Potterton models, E193 can be generated by a loss of communication signal between the PCB and the room thermostat — caused by loose wiring, a damaged cable, or a failing control board. This interpretation is less common but worth considering if the pump and pipework check out fine.
How to fix it
- Check the system pressure gauge DIY safe
Look at the pressure gauge on the front of your boiler. It should read between 1 and 1.5 bar when the system is cold. If it has dropped below 1 bar, top it up using the filling loop — a braided flexi-hose beneath the boiler with one or two valves. Open the valve(s) slowly until the pressure reaches around 1.2 bar, then close them securely. If you are unsure how to do this, your boiler manual will have a step-by-step guide.
- Bleed your radiators to release trapped air DIY safe
Turn off the boiler and let the system cool. Using a radiator bleed key, open the bleed valve on each radiator (starting upstairs and working down) until water — rather than air — trickles out, then close it again. Once done, recheck the system pressure as bleeding can cause a slight drop, and top up if needed.
- Check that your gas supply is active DIY safe
Confirm that your gas supply is turned on and that other gas appliances in your home (hob, oven) are working normally. If there is a wider gas supply issue, contact your gas supplier before doing anything else.
- Attempt a boiler reset DIY safe
Once you have checked pressure and bled radiators, try resetting the boiler using the reset button or procedure described in your manual. Do this no more than two or three times. If the E193 returns promptly each time, further resets will not help and you should move on to calling an engineer.
- Check thermostat wiring connections (if a communication fault is suspected) Gas Safe engineer
If your model is throwing E193 as a communication error rather than a clear pump fault, the wiring between the thermostat and the control board may be loose or damaged. Inspecting and reseating wiring connections on the PCB or control board must only be carried out by a Gas Safe registered engineer — do not attempt this yourself.
- Have the circulation pump inspected or replaced Gas Safe engineer
A Gas Safe registered engineer will test the pump for electrical continuity, check for mechanical seizure, and assess whether it needs to be replaced. Pump replacement is an internal boiler task and must not be attempted by an unqualified person.
- Commission a powerflush if sludge is suspected Gas Safe engineer
If the engineer finds evidence of heavy sludge or debris restricting circulation, a powerflush — using specialist equipment to push a cleaning chemical solution through the entire system — will clear the blockage. This should only be carried out by a qualified heating engineer, and fitting a magnetic system filter afterwards will help prevent recurrence.
- Call a Gas Safe registered engineer Gas Safe engineer
If the code persists after the DIY checks above, you need a professional diagnosis. A Gas Safe engineer will be able to test the pump, flow sensors, control board, and wiring methodically and carry out any necessary repairs safely. You can find a registered engineer at gassaferegister.co.uk.
Parts you may need
- Central heating circulation pump (e.g. Grundfos UPS2 or Wilo equivalent) · from £95
- Pump head seal / impeller kit · from £25
- Boiler PCB / control board · from £180
- Magnetic system filter (e.g. Adey MagnaClean) · from £65
- Thermostat wiring harness / connector · from £20
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–£400, depending on the underlying cause.
Frequently asked questions
Can I keep resetting my Potterton boiler to clear the E193 code?
Resetting two or three times is reasonable if you are troubleshooting, but repeatedly resetting without addressing the underlying cause will not fix the fault and could mask a more serious problem. If the code keeps coming back after a reset, stop and call a Gas Safe engineer — the boiler is locking out for a reason.
How much does it typically cost to fix a Potterton E193 fault in the UK?
For the most common repair — pump replacement — expect to pay roughly £150–£400 including parts and labour, with Checkatrade's average sitting around £275. If the system needs a powerflush to clear sludge, that adds £300–£650 depending on the size of your home. A PCB replacement, needed in rarer communication-fault cases, can push costs to £500 or more. If your boiler is over 10–12 years old, it is worth asking your engineer whether a replacement boiler makes more financial sense than an expensive repair.
Why are my radiators cold even though the boiler is running?
Cold radiators alongside an E193 are a strong sign that water is not circulating properly. The most likely culprits are a failing pump, trapped air (bleed your radiators), heavy sludge build-up, or low system pressure. Check the pressure gauge first — it should sit between 1 and 1.5 bar — and bleed your radiators. If heating is still poor after those checks, a Gas Safe engineer should assess the pump and system cleanliness.
What is the difference between the E193 as a circulation fault and as a communication error?
On most Potterton models, E193 flags a flow or pump problem — the boiler detects that water is not returning at the expected temperature, suggesting poor circulation. On a smaller number of models or configurations, the same code can indicate that the control board has lost its communication signal from the room thermostat, often due to loose wiring. A Gas Safe engineer can quickly determine which scenario applies to your boiler by checking the pump operation and wiring simultaneously.