A Potterton boiler showing an E133 fault code usually means the condensate pipe has frozen. When this happens, condensate cannot drain away correctly, so the boiler locks out to protect itself. In many cases the problem can be resolved safely at home. If the fault remains after resetting the boiler, you'll need a Gas Safe engineer to investigate further. If you're dealing with a different Potterton error, see our complete guide to Potterton boiler fault codes.
- Content Guide
- » What Does the Potterton E133 Fault Code Mean?
- » What Causes a Potterton E133 Fault?
- » How to Fix a Potterton Boiler E133 Fault Code
- - Step 1 – Confirm the Fault
- - Step 2 – Find the Condensate Pipe
- - Step 3 – Check for Freezing
- - Step 4 – Thaw the Pipe Safely
- - Step 5 – Reset the Boiler
- » When to Call a Gas Safe Engineer
- » How to Prevent the E133 Fault Returning
- » Need Help With a Potterton E133 Fault?
What Does the Potterton E133 Fault Code Mean?
The Potterton E133 fault indicates that condensate water cannot leave the boiler because the condensate pipe is frozen or blocked. As a safety measure, the boiler enters lockout mode until normal drainage is restored. This is most common during freezing weather.
What Causes a Potterton E133 Fault?
The most common cause is a frozen condensate pipe. This usually happens because temperatures fall below 0°C, the condensate pipe runs outside, insulation is missing or damaged, or poor pipe installation allows water to collect and freeze. These conditions stop condensate draining correctly, causing the boiler to shut down.
How to Fix a Potterton Boiler E133 Fault Code
Step 1 – Confirm the Fault
Check the display shows E133 before carrying out any checks.
Step 2 – Find the Condensate Pipe
Locate the plastic waste pipe running from the boiler to an external drain or waste pipe.
Step 3 – Check for Freezing
Look for visible ice, swollen sections, no water leaving the pipe, or unusual gurgling noises.
Step 4 – Thaw the Pipe Safely
Never pour boiling water onto the pipe. Instead use lukewarm water, warm towels, a hot water bottle or a hair dryer on a low setting. Once thawed, make sure condensate can drain freely.
Step 5 – Reset the Boiler
Once the blockage has cleared, allow the pipe to drain, hold the reset button for around 3–5 seconds, wait for the boiler to restart, and check that the fault does not return.
When to Call a Gas Safe Engineer
Arrange professional help if the condensate pipe has cracked, you cannot safely reach the pipe, E133 returns after resetting, or the pipe needs relocating or insulating properly. A recurring E133 fault can point to an installation issue rather than cold weather alone. If your boiler still won't restart, our boiler repair service in London can diagnose the fault and carry out any necessary repairs.
How to Prevent the E133 Fault Returning
You can reduce the chance of another E133 fault by insulating exposed condensate pipes, improving external pipe routing where practical, keeping the pipe outlet clear, and booking annual servicing. Routine servicing allows potential drainage problems to be identified before winter.
Need Help With a Potterton E133 Fault?
If thawing the condensate pipe hasn't cleared the fault, or the boiler keeps locking out, arrange a Gas Safe engineer to investigate. A proper repair will identify the underlying cause and help prevent repeat breakdowns.
