No Hot Water from Your Boiler System
Losing hot water from a boiler system is different from losing heating. Depending on your system type, the cause may involve the boiler itself or a separate component.
Urgency: Medium to high urgency
Possible Causes
- Combi boiler diverter valve failure
- Indirect water tank sensor or thermostat failure
- Tankless coil failure (older systems)
- Boiler not firing when hot water is demanded
- Mixing valve problem
- Circulation pump for domestic hot water not running
Safe Homeowner Checks
These observations do not require touching the equipment.
- Determine if you have a combi boiler (no separate tank) or a system with a hot water cylinder
- Check if the boiler fires when you turn on a hot water tap
- Note whether heating is still working (this helps identify the problem area)
Next Steps
- If your combi boiler provides no hot water but heating works, the diverter valve may have failed
- If neither heating nor hot water work, the boiler itself may have a more general problem
- If you have a separate hot water tank, check if there is power to it
Safety Reminder
If you smell gas, suspect carbon monoxide or believe there is an immediate danger, leave the property and contact emergency services or the appropriate gas emergency authority. Do not remain inside — exit the building immediately and call for help from outside.