Heating systems · Homeowner answer
Why are my radiators cold at the bottom?
Short answer
Cold at the bottom usually means sludge — magnetite from corrosion — has settled in the radiator. Cold at the top usually means air, which bleeding fixes.
What changes the answer
- where on the radiator it is cold
- how many radiators are affected
- the colour of the water when you bleed one
What you can check yourself
- bleed the radiator and note whether the water is clear or dark
- check whether the boiler makes kettling or banging noises
What to do next
Sludge across several radiators is a power-flush job, followed by a magnetic filter and inhibitor to stop it building up again.
This page gives general information only. Christy needs to see your system — in person or from your photos — before he can give you firm advice or a price.