Radiator cold — top, bottom, or completely?
Where the radiator is cold tells you almost everything: cold at the top = trapped air, cold at the bottom = sludge, cold all over on one rad = a stuck TRV or lockshield. Two-minute triage below.
Make it safe — before anything else
Only Gas Safe registered engineers work on gas
Anything on the boiler side is Gas Safe. Bleeding, TRV heads and lockshields are safe DIY when the heating is off and the radiator is cool.
Cool it down first
Never bleed a radiator with the pump running or the water hot — you'll get scalded. Turn the boiler off and let the radiator cool for 20 minutes.
What Kevin (our AI) will check first
Message Kevin and he'll ask exactly these questions before we send an engineer, so we bring the right parts on the first van.
- Which radiator (upstairs / downstairs / room name)?
- Cold at the top, bottom, or all over?
- How many radiators are affected?
- When was the system last flushed or serviced?
- Do you have magnetic filters (MagnaClean / Adey) fitted?
Common causes of a cold radiator
Trapped air (bleeding fixes)
Air rises to the top of the radiator, water sits below. Bleed key, quarter turn, close as soon as water appears. Re-top pressure to 1.2 bar.
Magnetite sludge in the bottom
Rust and debris settles in the bottom of radiators. Powerflush or a targeted chemical flush restores full output. Typical £480 – £780 for a full-house flush.
Seized TRV pin
Under the plastic head, the brass pin sticks down. Head off, gentle tap and a squirt of releasing spray usually frees it. Otherwise £70 – £110 to replace the valve body.
Closed or wrong-balanced lockshield
Lockshield on the far end sets the flow rate. If it's shut or badly set, that radiator never warms up. Free rebalance during any diagnostic visit.
Failed motorised zone valve
On system boilers, a failed zone valve can leave a whole floor cold. £150 – £240 fitted.
Honest cost band — why we won't quote blind
Typical
£90 – £160 for TRV swap, single radiator flush or full system balance
Complex
Full magnetic filter fit £190 – £280. Powerflush £480 – £780. Motorised valve £150 – £240.
£50 diagnostic gets you a real answer — bleed, balance, flush or replace — and a written fixed price for any work.
Fixed £50 diagnostic
Flat fee. No hourly meter running.
Fair quote or refund
Transparent pricing — refunded if we don't fix it.
Vetted UK engineers
DBS-checked, insured, real reviews.
AI-triaged in seconds
KJ chats first so the right engineer arrives.
Related emergencies
Boiler on but no heating
Emergency guide
Boiler kettling
Emergency guide
Boiler losing pressure
Emergency guide
See all in the emergency plumbing hub — or the leaks & water damage hub.
Areas we cover for cold radiator
Same-day across Greater Manchester and Rochdale.
Cold radiator — FAQs
Dealing with a cold radiator? Chat with Kevin now
Real triage in seconds. £50 diagnostic visit — refunded if we don't fix it.
Related hubs: emergency plumbing, leaks & water damage, all services.
Chat with Kevin about Cold radiator