Why Are My Radiators Only Warm at the Top in Bordon?
If you live in Bordon or the neighbouring areas like Alton, Liphook or Farnham, you might notice that your radiators get toasty at the top but remain cold at the bottom. This common issue is almost always down to trapped air inside the radiator, which stops hot water from circulating fully. In homes across GU35, GU32 and GU34 postcodes, this can lead to chilly spots and uneven heat distribution.
Understanding Trapped Air and Its Effects
When your central heating system heats up, hot water is pumped through the radiators. Air pockets act like a barrier to water flow, so the warm water can’t reach the lower sections. Here’s what happens:
- Cold patches at the bottom of the radiator
- Hot flush at the top where water gathers
- Increased energy use as your boiler works harder
- Noise from gurgling or bubbling sounds
Left unchecked, trapped air can cause corrosion, leaks or even a heating breakdown that needs a professional boiler repair.
Diagnosing Radiator Problems
1. Feel the Temperature Gradient
Starting at the valves, use your hand or a non-contact thermometer to check how the temperature changes from top to bottom. A significant drop in warmth indicates an air pocket.
2. Listen for Sounds
Gurgling or trickling noises when the heating is on are a clear sign of air in the system. This is most common on first firing after boiler servicing or new installation.
3. Inspect the Pressure Gauge
Low system pressure on your boiler readout can let air be drawn into radiators. If it’s consistently below the recommended 1–1.5 bar, top up your system or arrange a boiler servicing.
How to Bleed Your Radiators: A Step-by-Step Guide
What You’ll Need
- Radiator key (or flat screwdriver for modern valves)
- A cloth or small container to catch water
- A towel or protective pad for the floor
Step 1: Switch Off Your Heating
Ensure your boiler is off and radiators are cool so you won’t scald yourself. This is vital for safety.
Step 2: Locate the Bleed Valve
The valve is usually at the top corner of the radiator. It’s a square or slotted screw head.
Step 3: Loosen the Valve
Turn the key or screwdriver anti-clockwise just a quarter turn until you hear a hissing sound. This is air escaping. Have your cloth or container ready to catch drips.
Step 4: Close the Valve
Once water begins to trickle out steadily, tighten the valve clockwise. Wipe away any excess water immediately.
Step 5: Check Boiler Pressure
After bleeding several radiators, your system pressure may drop. Top it up using the filling loop following the boiler manufacturer’s instructions or call a boiler cover engineer if you’re unsure.
Preventing Trapped Air and Future Issues
- Regularly schedule boiler servicing to catch leaks and pressure drops early.
- Keep your system filter clean to reduce sludge build-up.
- Use inhibitor chemicals when installing a new boiler to prevent corrosion.
- Top up your heating system pressure after bleeding radiators.
Annual checks help maintain efficiency, reduce energy bills and extend the life of your heating system—whether you’re in GU30 Haslemere, GU35 Petersfield or nearby Whitehill.
When to Call a Professional Gas Safe Engineer
If bleeding your radiators doesn’t resolve the issue, or if you spot leaks, persistent low pressure or noisy cold spots, it’s time to contact a qualified engineer. They can diagnose deeper faults, carry out a powerflush or advise on a new boiler installation if yours is ageing or underperforming.
Frequently Asked Questions
Q: How often should I bleed my radiators?
A: Most homeowners bleed radiators once a year before winter. If you hear gurgling or notice cold spots, you can do it anytime the heating is off and the system is cool.
Q: Can trapped air damage my boiler?
A: Indirectly. Air pockets may cause uneven circulation and pressure fluctuations, forcing the boiler to work harder and leading to wear over time. Regular bleeding and service checks prevent this.
Q: I’ve bled the radiator but it’s still cold at the bottom. What now?
A: There may be sludge or limescale blocking flow. A powerflush or hiring a Gas Safe engineer for a deep clean is recommended.
Need Help with Your Radiators?
If you need help with your heating or boiler, our local engineers are here to help. Call us on (01420) 558993 or book online.
Written by Embassy Gas — your local heating experts covering Bordon, Alton, Liphook, Farnham and surrounding areas.