Turn the heating off and allow the system to cool before bleeding or adjusting radiators
Radiators contain hot pressurised water. Stop if a fitting is seized, leaking heavily or boiler pressure repeatedly drops.
MOST LIKELY CAUSES
Start with these
Valve gland leak
Water may appear around the spindle.
Compression joint leak
The nut and olive connection may seep.
Bleed valve leak
A damaged vent or seal can drip.
Panel corrosion
Rust can create pinholes in the radiator body.
Symptom variations Match the exact heat pattern, sound or leak position. ⌄
- Drip from valve
- Wet patch beneath radiator
- Rust mark on panel
- Pressure keeps dropping
- Leak worsens when heating is on
Quick checks Simple checks before removing fittings. ⌄
- Confirm the heating is on.
- Check whether one radiator or the whole system is affected.
- Inspect TRV and lockshield positions.
- Look for leaks, air and corrosion.
- Let the system cool before bleeding.
Step 1 — Turn off heating and contain the leak Turn the heating off and allow the radiator to cool first. ⌄
Place towels or a tray underneath and let the system cool.
Step 2 — Find the exact source Turn the heating off and allow the radiator to cool first. ⌄
Dry the area and watch the valve, vent, tail and panel.
Step 3 — Isolate if safe Turn the heating off and allow the radiator to cool first. ⌄
Close both radiator valves and arrange repair.
Common causes explained Why radiator faults develop. ⌄
Radiator leaks commonly come from valve glands, compression joints, bleed vents, tails, rusted panels or disturbed pipework.
Advanced diagnostics Heating-engineer checks and repair work. ⌄
- Repack or replace valve gland.
- Remake compression joint.
- Replace bleed valve or tail.
- Pressure-test or replace radiator.
Parts that may need replacing Common components linked to this fault. ⌄
- TRV
- Lockshield valve
- Bleed valve
- Radiator tail
- Radiator
When to call a heating engineer Conditions that should end basic troubleshooting. ⌄
- Boiler pressure keeps dropping.
- A radiator or valve is leaking heavily.
- Valves are seized or corroded.
- Several radiators remain cold.
- The pump or boiler may be faulty.
Frequently asked questions Common radiator questions. ⌄
Should I bleed radiators while heating is on?
No. Turn the heating off and allow the system to cool first.
Why did boiler pressure drop?
Releasing air can reduce pressure in a sealed system.