BoilerFaultCodesThe 6 most common faults
Your boiler is struggling to move water around your heating system, likely because the pressure is too low or a valve is blocking the flow.
Check your boiler pressure gauge; if it is below 1 bar, use the filling loop to top it up to 1.5 bar.Ensure all radiator valves (TRVs) are fully open to allow water to circulate freely.Restart the boiler using the reset button once the pressure is correct.
Your boiler is struggling to push water through your heating system, usually because there is trapped air, a blockage, or a pump failing to circulate the water.
Check that all radiator valves throughout your home are fully open.Check your boiler pressure gauge to ensure it reads between 1.0 and 1.5 bar, topping it up via the filling loop if necessary.Bleed all radiators to remove any trapped air that may be preventing flow.
Your boiler is struggling to push water around your heating system because the flow is too restricted or the pressure is too low.
Check that all your radiator valves are fully openEnsure your system water pressure is set between 1.0 and 1.5 bar on the boiler displayCheck if any air needs to be bled out of your radiators using a radiator key
Your boiler is struggling to move water around your heating system correctly, which is preventing it from working as it should.
Check your radiator valves are fully openCheck the central heating system pressure gauge on the front of the boiler is between 1 and 1.5 barIf the pressure is low, use the filling loop to top it up to 1.5 barEnsure your central heating pump is not seized or stuck
Your boiler has detected that water is not moving around your heating system fast enough, triggering a safety shut-off to prevent overheating.
Check your boiler pressure gauge and top it up to 1.5 bar using the filling loop if it is below 1 bar.Ensure all radiator thermostatic valves are fully open to allow water to circulate freely.Check that any external heating system filters are not blocked and the central heating pump is audibly running.
Your boiler is struggling to move enough water through your heating system, which usually means there is a blockage, air trapped in the pipes, or a pump struggling to work.
Check all radiator valves are fully open.Ensure your system pressure is set correctly between 1.0 and 1.5 bar.Bleed all radiators in the house to release any trapped air.
on the Ariston Clas One
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 Ariston 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