Ignite Plumbing & Heating
Radiator Cold at the Bottom? Causes and Fixes in Norwich Homes
Cold patches at the bottom of your radiator almost always mean sludge. Here's what's happening and how we fix it.
What causes a cold bottom?
The most common cause is magnetite — black iron oxide sludge that forms as your steel radiators slowly corrode internally. Over years, this settles at the base of the radiator and prevents hot water from circulating to the bottom section.
How to confirm it's sludge
Put your hand on the middle and bottom of the radiator. If there's a clear temperature drop toward the base, and the top is hot, it's almost certainly sludge. Bleed the radiator — if black or discoloured water comes out, that confirms it.
Can I fix it myself?
You can try isolating and removing the radiator to flush it with a hose, but this rarely solves the problem long-term — the sludge is throughout the system, not just in that one radiator. It'll be back within months.
The proper fix — power flush
A professional power flush circulates high-velocity cleaning chemicals through the entire system, breaking up and flushing out all the accumulated sludge. Followed by a magnetic filter, this is a permanent solution.
Magnetic filter — why it matters
A magnetic filter (MagnaClean or equivalent) captures magnetite particles as they circulate before they can settle in radiators. Fitted to any system, it prevents sludge from ever building up again. We include one in all power flush quotes.