BoilerFaultCodesThe 6 most common faults
Your boiler has stopped working because the water pressure inside the system has risen too high, likely due to a faulty filling loop or a system issue.
Locate the radiator bleed valves throughout your home.Place a cloth under a valve and use a radiator key to slowly release some water until the pressure gauge on the boiler drops to between 1.0 and 1.5 bar.Check the boiler control panel to see if the error has cleared.
Your boiler has detected that the water pressure inside your heating system is either too low or too high for it to operate safely.
Check your pressure gauge, which should ideally read between 1.0 and 1.5 bar.If the pressure is below 1.0 bar, locate the filling loop under the boiler.Slowly open the valve to let water in until the pressure reaches 1.5 bar, then tightly close it.If the pressure was above 2.5 bar, you may need to bleed a radiator to release excess pressure.
Your boiler has stopped working because the water pressure inside the system has dropped too low to operate safely.
Locate the external filling loop, which is a silver braided flexible hose connected to two valves beneath the boiler.Slowly open both valves to allow mains water to enter the system while watching the pressure gauge on the front of the boiler.Once the needle reaches the green zone (ideally 1.5 bar), tightly close both valves to stop the water flow.
Your boiler is struggling to pump water around your heating system correctly, so it has turned itself off to avoid overheating.
Full guide for 154Your boiler is struggling to detect the movement of water inside the system, which is preventing it from heating your home or water safely.
Full guide for 20Your boiler is struggling to accurately measure the temperature of the water returning to it, which prevents the system from heating your home properly.
Full guide for 40on the Atag S 25CR
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