BoilerFaultCodesThe 6 most common faults
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.
Your boiler is struggling to move water around your heating system effectively, usually due to low pressure or trapped air.
Check your boiler's pressure gauge and ensure it is between 1 and 1.5 barIf the pressure is low, use the filling loop to top it up to the correct levelBleed your radiators to release any trapped air that may be blocking the flow
Your boiler has detected that the water pressure inside your heating system is too high, which can put unnecessary strain on the internal components.
Locate a radiator in your home with a bleed valve.Place a cloth and a container underneath the valve.Open the bleed valve slowly to release air and water until the pressure gauge on the front of the boiler drops to between 1 bar and 1.5 bar.
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
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Affiliate links. We may earn a commission at no extra cost to you.