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Boiler component guide

Boiler Diverter Valve

The diverter valve helps a combi boiler switch between heating and hot water demand. When it sticks or fails, the boiler may struggle to send heat where it is needed.

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What the diverter valve does

On many combi boilers, the diverter valve directs heat either to the radiators or to the hot water circuit depending on what the property is calling for.

How failure shows up

When the valve sticks, wears out or does not switch cleanly, you can end up with poor hot water performance even though other parts of the system still seem to work.

What the repair usually involves

The first step is to confirm that the diverter valve is genuinely at fault. Once confirmed, the repair may involve replacing the valve or associated parts.

Frequently asked questions

Can this part always be repaired instead of replaced?

Not always. Some parts can be adjusted or re-pressurised, but many failed components need replacing once they are confirmed faulty.

Will replacing one part solve the whole issue?

Often it will, but the right answer depends on proper diagnosis. Symptoms like low pressure or no hot water can be caused by more than one component.

Should I book an engineer if the boiler still works sometimes?

Yes. Intermittent faults usually point to a part that is deteriorating and can lead to a full breakdown if ignored.

Related pages

Need a repair visit?

Book a boiler repair call-out

If the failed part is affecting heating, hot water or boiler pressure, we can diagnose the fault and advise on repair versus replacement.

Signs it may have failed

  • Heating works but hot water does not
  • Hot water is inconsistent or lukewarm
  • Boiler responds slowly when switching demand