Potterton E119 Fault Code
The E119 fault is the most homeowner-accessible Potterton fault — system pressure has dropped below the minimum operating threshold. Usually resolved by repressurising via the filling loop to 1.2–1.5 bar. If pressure drops again within weeks, a leak or failed expansion vessel is the underlying cause.
What is the Potterton E119 fault code?
The Potterton E119 fault is triggered when the pressure sensor detects the central heating circuit has fallen below the minimum threshold — typically 0.5 bar on Titanium, Gold, and Promax models. The boiler locks out to prevent running dry and potentially damaging the heat exchanger or pump. Repressurising via the filling loop clears E119 immediately in most cases. If pressure drops again within weeks, there is a leak or the expansion vessel has failed. Because Potterton shares the BDR Thermea platform with Baxi, the E119 code and the pressure monitoring system are identical across both brands.
What causes the E119 fault?
All sealed systems lose a small amount of pressure over time. A drop of 0.1–0.2 bar per year is normal. Below 0.5 bar, the Potterton boiler locks out with E119.
A dripping radiator valve, weeping pipe joint, or leaking pump gland causes pressure to drop more rapidly. Pressure dropping more than 0.5 bar within weeks of repressurising points to a leak.
A depleted air charge in the expansion vessel causes pressure to drop dramatically on cooling — often falling below the E119 threshold overnight.
Bleeding radiators releases water alongside air. Always repressurise via the filling loop after bleeding.
A stuck-open automatic air vent slowly allows water to escape, gradually dropping system pressure.
If both filling loop valves are not fully closed after repressurising, the loop can drain back and cause pressure to fall.
What you can safely check yourself
Cold system pressure should be 1.0–1.5 bar. Below 0.8 bar, repressurise. If the gauge reads zero, check for visible leaks under the boiler and at radiator valves before filling.
Locate the filling loop under the boiler — two valves on a short braided hose. Open both valves slowly until the gauge reads 1.2–1.5 bar, then close both valves fully.
Hold the reset button for 3 seconds. Monitor the pressure gauge over the next 48–72 hours. If pressure drops more than 0.3 bar within a week, call a Gas Safe engineer.
Do not reset the boiler more than once if the fault code returns immediately. Repeated resets without diagnosis can mask a worsening fault.
What needs a Gas Safe engineer
- Pressure test the system to locate any hidden leak
- Inspect the expansion vessel air charge and recharge or replace if failed
- Check automatic air vents and replace if weeping
- Inspect pump gland seals for seepage
- Check radiator valve gland nuts at each radiator
- Replace filling loop or internal valves if leakage is confirmed
- Commission and pressure test after any repair
Expansion vessel failures are common across South London, where Thames Water's hard water accelerates corrosion of the rubber diaphragm inside the vessel. Potterton Gold and Titanium boilers in Wandsworth, Merton, Lewisham, Lambeth, Southwark, Greenwich, and Bromley frequently develop expansion vessel faults alongside E119 after 10–12 years. Reion checks expansion vessel pressure on every annual service in South London.
How much does a E119 repair cost?
Costs below are UK averages. Reion provides a fixed quote after the £80 diagnostic visit — no obligation to proceed.
How to reset a Potterton boiler showing E119
Repressurise to 1.2 bar via the filling loop before resetting.
Ensure both filling loop valves are fully closed.
Hold the reset button for 3 seconds.
Monitor the pressure gauge over the next 48 hours.
If pressure drops again within days, call a Gas Safe engineer.
E119 alone is very rarely a reason to consider replacing a Potterton boiler. The exception is if a pressure test reveals a cracked heat exchanger as the source of the pressure loss — a fault that makes repair uneconomical on older boilers.
Common questions about the Potterton E119 fault
Can I fix a Potterton E119 fault myself?
Why does my Potterton boiler keep showing E119?
What pressure should a Potterton boiler be at?
How much does a Potterton E119 repair cost in London?
Is the Potterton E119 the same fault code as Baxi E119?
Other Potterton fault codes
Need a Potterton engineer in London?
Reion is Gas Safe registered (919881), based in South London, and available 24/7. Fixed price after the diagnostic visit — no hidden charges.
