No Central Heating But Hot Water Working? Causes & Fixes UK
If hot water works but radiators do not heat, controls, diverter valves, motorised valves, pumps, or low pressure may be involved. This guide outlines common UK causes and next steps.
Controls and Thermostat
Confirm heating is on in the programmer and the room thermostat calls for heat. Try a higher setpoint or override.
Motorised Valves
On many system setups a stuck valve can allow hot water but block heating—usually engineer work.
Combi Diverter Valve
A diverter stuck toward domestic hot water can prevent heating circulation even when the boiler fires.
Pump and Pressure
Low sealed-system pressure or pump failure can stop circulation—check the gauge and listen for pump operation.
Get the Right Boiler Size for Your Home
Our free boiler size calculator uses your property details, radiator count, insulation and hot water needs to recommend a suitable kW range. No sign-up required—get results in seconds.
Use the Boiler Size CalculatorFrequently Asked Questions
Can low pressure stop heating only?
Sometimes—depends on boiler logic and fault state.
Is a stuck diverter expensive?
Costs vary by boiler model and labour.
Should I bleed radiators?
If air is suspected; recheck pressure on sealed systems.
Could it be the thermostat batteries?
Yes for wireless stats—replace and retest.
When to call an engineer?
If basic checks fail or you are unsure—use Gas Safe for gas appliances.