Common boiler problems.

Your annual service will also be able to identify any of these common problems. Found and corrected early, they will significantly prolong the life of your boiler. 

1. Faulty automatic air vent

Dripping or a build-up of scale at the vent that releases air from the boiler to outside. This should be spotted during a service.

Solution: Replace the vent

2. Limescale build-up in central heating pipes

This is most common in hard-water areas. It can lead to blockages and cause fluctuations in temperature of hot water taps.

Solution: Fit a scale reducer, ideally this should happen when a new boiler is installed. 

3. Faulty or blocked pressure relief valve

This may cause constant dripping from the copper pipe leading to the external wall.

Solution: Replace the pressure relief valve 

 4. Pump failure

If this packs up, it would leave you with no heating or hot water. Bad news at any time, particularly in winter. It is caused by sludge in the system, or old age.

Solution: Replace the pump 

 5. Faulty diverter valve

The system may get 'stuck' on hot water or central heating.

Solution: Replace the diverter valve

 6. Sludge in the system

Radiators are hot at the top with cold spots at the bottom.

Solution: The system may need a powerflush, but this is costly and not always the best solution. Don't get one until you have got several opinions to be sure it's needed.

7. Faulty expansion vessel. The system pressure increases above 3 bar with the heating on and the relief pipe starts dripping.

Solution:  Replace the expansion vessel or pump up the vessel if the expansion air has depleted. 


All these details are for a gas combination boiler – the most common type of boiler in the UK.