Finding that your heating works but you have no hot water can be frustrating, especially when everything else in your home seems to be running as normal. This guide explains the most common causes, simple checks you can do yourself, and when to call a Gas Safe engineer. Homeowners across areas such as Bordon, Whitehill, Liphook, Alton and Farnham often experience these symptoms during colder months, so the steps below are designed to help you narrow down the fault quickly.
Quick checks you can do now
Before assuming there is a major issue, a few simple checks can help rule out common problems.
- Make sure your hot water demand is set on the programmer.
- Confirm your boiler is not showing a fault code.
- Check that the hot water cylinder thermostat is not turned too low.
- Listen to see if the boiler fires when you turn on hot water.
Here is a quick checklist to run through:
- Water supply on?
- Boiler pressure between 1.0 and 1.5 bar?
- Any recent power cuts?
- Hot water taps fully open?
Common reasons for no hot water
It might feel confusing when radiators heat up normally, yet hot water won’t run warm. The underlying causes are often confined to the hot water side of your system rather than the heating circuit.
- Diverter valve stuck: A very common issue on combination boilers. If the diverter valve sticks in the heating position, the radiators warm up but no hot water flows.
- Faulty cylinder thermostat: In system and heat-only boilers, the cylinder stat may not be requesting heat even when the temperature drops.
- Motorised valve issue: Two-port or three-port valves control heating and hot water flow. If the hot water valve fails, you may get heating only.
- Airlock in the hot water pipework: This is more likely in older properties around GU35, GU34 and GU9 postcodes, where pipework layouts vary.
- Boiler sensor or plate heat exchanger issue: Combination boilers rely on sensors to detect demand and route heat properly. A failure here may affect hot water but not heating.
Understanding your system type
The type of heating system you have affects the likely cause. Many homes in Haslemere, Bordon and surrounding areas use combination boilers, while older homes may use a hot water cylinder. Understanding which system you own helps narrow down the fault.
- Combination boilers: If you have instant hot water with no cylinder, the most common causes include diverter valve failure or blocked plate heat exchangers.
- System or heat-only boilers: These rely on stored hot water in a cylinder. Problems often involve motorised valves, the cylinder thermostat or wiring centre connections.
No hot water but radiator heating works
This situation is common, and the phrase no hot water but radiator heating works usually points to a component dedicated to the hot water supply. With radiators functioning normally, your boiler is successfully generating heat, but the system is failing to send that heat to your taps or cylinder.
Checks specific to combination boilers
Combination boilers supply hot water on demand, so any disruption can quickly affect your taps. If homes in Liphook or Alton report heating working but no hot water, the diverter valve is often the culprit. This valve shifts between heating and hot water; when stuck, it may prioritise heating only.
Other checks include:
- Running a different hot tap to see if the issue is isolated.
- Checking for fluctuating boiler pressure, which may prevent hot water generation.
- Listening for clicking or buzzing inside the boiler, which may indicate a valve attempting to move.
Checks for system and heat-only boilers
These systems use a hot water cylinder. A common sign of a motorised valve fault is when the heating turns on even if only hot water is selected on the programmer. This suggests the valve is not directing flow correctly. Homes in older parts of Bordon and Whitehill often still rely on these systems, making these checks especially useful.
- Feel the pipes going into the cylinder; the flow pipe should heat up during a hot water demand.
- Listen for the motorised valve moving when switching between heating and hot water.
- Check the cylinder thermostat is set between 55 and 60 degrees.
When DIY checks are not enough
While many of the checks above are safe for homeowners, any internal boiler work must be handled by a Gas Safe engineer. Stuck valves, wiring faults, failed thermistors and blocked heat exchangers require proper diagnostics and tools. If you are in Haslemere, Bordon or nearby areas such as Alton or Farnham, a professional assessment will quickly determine whether the issue is mechanical, electrical or related to system flow.
Next steps
If you’ve completed the checks above and still have no hot water, you can book a professional visit at https://www.embassygas.com/book