Keston Diverter Valve Cross-Leak or Stuck Position

Radiators get hot when only hot water is demanded, or hot water is poor when heating is on

Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Worn diverter valve seals, Sticking diverter spindle, Faulty diverter actuator, Debris in valve body

How to Fix / Troubleshooting

Safety: Pipework may be hot. Allow system to cool before touching valves.

User actions:

Note when the issue occurs (e.g., radiators warming during summer when only DHW is used) and inform the engineer.

Engineer actions:

Test the Keston diverter valve operation by observing actuator movement between CH and DHW demands.
Remove the actuator and manually move the valve spindle; if stiff or leaking across, replace the valve body.
Inspect for debris or scale in the valve and flush the system if contamination is present.
Replace the diverter actuator if it fails to drive the valve correctly.

Repair Difficulty

Hard 4/5

Required Part

Diverter Valve Assembly

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