BoilerFaultCodesThe 3 most common faults
Your boiler has detected that the water pressure inside the system is far too high, causing it to shut down for safety.
Why it happens: This fault occurs when there is too much water forced into your heating system, often because the filling loop valves have been left slightly open or have developed a leak. It can also be caused by a failure in the expansion vessel, which is the internal part responsible for managing the natural pressure changes that happen when water gets hot.
Check that the filling loop valves are fully closedBleed water from a radiator using a bleed key to reduce system pressureMonitor the pressure gauge until it returns to between 1.0 and 1.5 barPress the reset button to restart the boiler
Your boiler has detected that the water pressure is too low for it to operate safely, or it is struggling to move water through the system.
Why it happens: This fault occurs when the boiler's internal sensors detect that the system lacks the minimum water pressure required to circulate heat safely. The most common reason is a slow leak somewhere in the pipework or radiators, but it can also be triggered if the pump has failed and can no longer push water through the heat exchanger.
Check the pressure gauge on the front of the boiler; it should ideally be between 1.2 and 1.5 bar.Locate the filling loop (usually a silver braided hose with small black lever valves) underneath the boiler.Slowly open the valves to let water in until the gauge reaches 1.5 bar, then ensure they are closed tightly.Press the Reset button on the control panel to clear the fault.
Your boiler has detected a problem with the sensor that manages your hot water temperature, which may result in your taps running cold or having inconsistent heat.
Why it happens: This fault occurs when the internal sensor responsible for monitoring your hot water temperature has failed or is sending an incorrect signal to the main control board. The most common reason is that the sensor has suffered electrical wear over time or the wiring connecting it to the boiler's computer has come loose or corroded.
Full guide for 50on the Atag iC Economiser 25
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Atag shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue