Introduction
It’s the middle of winter in Bordon (GU35), you switch on the heating and your radiators warm up perfectly – but there’s no hot water for your shower or taps. This frustrating scenario is all too common in Bordon, Alton, Liphook and nearby areas. In this guide, we’ll explore the most common hot-water-only failures, explain simple troubleshooting steps and highlight when you should call a Gas Safe engineer.
Common Causes of Heating But No Hot Water
1. Faulty Diverter Valve
The diverter valve directs hot water either to the central heating or to your taps. If it sticks in the heating position, you’ll get heat but no domestic hot water. This is a common issue in older combi boilers:
- Symptoms: Radiators heat up, but taps run cold.
- DIY Check: Turn off the boiler, let it cool, then gently tap the valve body to free any debris.
- Solution: If tapping doesn’t help, you’ll need a qualified engineer to replace or service the valve.
2. Airlock in Hot Water System
An airlock happens when air gets trapped in the hot water feed pipe, blocking the flow. This often affects taps nearest the boiler:
- Symptoms: Weak flow or no flow at specific taps only.
- DIY Check: Open the tap at full flow and ask someone to switch the boiler on and off a few times to force water through.
- Solution: Persistent airlocks may require a professional Power Flush of your system.
3. Limescale Build-Up
Hard water in Farnham and Liphook areas can lead to limescale in heat exchangers or showers. Over time, this blocks water flow:
- Symptoms: Gradual reduction in hot water flow and temperature.
- DIY Check: Inspect shower heads and taps for scale; descale with vinegar or a descaler product.
- Solution: If internal boiler components are scaled up, a Gas Safe engineer can fit a magnetic filter or perform a chemical flush.
4. Faulty Thermostat or Temperature Sensor
Modern boilers use sensors to regulate hot water temperature. A failed sensor may tell the boiler it’s already at temperature, shutting off the heat:
- Symptoms: Boiler cycles on and off with no hot water output.
- DIY Check: Reset the boiler and check error codes on the display.
- Solution: Sensor replacement is a job for a qualified engineer.
5. Malfunctioning Immersion Heater (If Present)
Some homes with system or conventional boilers also have an immersion heater in the hot water cylinder. A blown fuse or faulty element stops hot water production:
- Symptoms: No hot water but heating unaffected.
- DIY Check: Check the fuse box for a tripped switch labelled “immersion heater”.
- Solution: If the switch keeps tripping, or the element is dead, contact an electrician and a heating engineer.
6. Broken Motorised Valve
In a system boiler setup, motorised valves control flow to heating or hot water cylinders. A single or mid-position valve fault can isolate hot water:
- Symptoms: No hot water, heating still works.
- DIY Check: Listen for a clicking sound when calling for hot water.
- Solution: Valve replacement by a Gas Safe engineer is usually required.
7. Boiler Pressure Issues
Low boiler pressure can limit hot water production. Many boilers cut out domestic hot water if pressure drops below 1 bar:
- Symptoms: Boiler shows low-pressure warning, no hot water.
- DIY Check: Check the pressure gauge; if below 1 bar, top up via the filling loop.
- Solution: If pressure keeps dropping, a leak or faulty pressure relief valve may need professional repair.
8. Electrical Faults or PCB Failure
The boiler’s printed circuit board (PCB) controls combustion and water flow. A fault here might disable hot water circuits:
- Symptoms: Boiler displays fault codes or fails to heat water.
- DIY Check: Note any error code and consult the manual.
- Solution: PCB replacement and electrical checks must be carried out by a Gas Safe registered engineer.
Troubleshooting Steps for Homeowners
Before calling for service, you can run through these checks:
- Reset your boiler and check display codes.
- Inspect boiler pressure and top up if needed.
- Bleed radiators to ensure the system is free of air.
- Check immersion heater switch and fuses if applicable.
- Descale taps and shower heads to rule out limescale blockages.
If these steps don’t restore hot water, it’s time to call a qualified professional.
When to Call Our Gas Safe Engineers
For reliable solutions in Bordon, Whitehill, Haslemere and surrounding GU35 areas, our team can help with:
- Hot water repairs and diverter valve replacement.
- System Power Flush to eliminate debris and limescale.
- New boiler installation: consider upgrading to an efficient combi boiler for uninterrupted hot water here.
- Annual boiler servicing to catch issues early and maintain warranty book your service.
- Comprehensive boiler cover plans to protect you against unexpected breakdowns learn more.
Frequently Asked Questions
Q: Why does my heating work but no hot water?
A: Usually a stuck diverter valve, airlock or low pressure prevents domestic hot water flow. A Gas Safe engineer can diagnose and replace the faulty part.
Q: Can I fix a stuck diverter valve myself?
A: You can try gently tapping the valve body after switching off and isolating the boiler, but replacement should be done by a qualified engineer.
Q: How often should I service my boiler?
A: Annual servicing by a Gas Safe registered engineer ensures optimal performance and helps prevent hot water failures.
If you need help with your heating or boiler, our local engineers are here to help. Call us on (01420) 558993 or book online at embassygas.com/book
Written by Embassy Gas — your local heating experts covering Bordon, Alton, Liphook, Farnham and surrounding areas.