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Cold At The Bottom, Warm At The Top: That's Sludge, Not A Faulty Radiator
Black sludge, magnetite, builds up inside a central heating system over years, and it settles at the bottom of radiators first, which is exactly why that's where the cold patch shows up.
Left alone, it makes the boiler work harder to heat the same house, causes the banging and gurgling noises people usually blame on the boiler itself, and can genuinely affect a new boiler's warranty if it's fitted onto a dirty system without one.
A power flush forces cleaning chemicals through the entire system under pressure, not just the radiator that's showing the symptom, since the sludge causing one cold radiator today is sitting in the pipework everywhere else too.
What Happens When You Call
Test the system water first
Confirms sludge is actually the cause before committing to a flush, rather than assuming every cold radiator needs one.
Flush the whole system
Cleaning chemicals forced through every radiator and pipe run under pressure, not just the affected one.
Fit or check a magnetic filter
Catches the sludge that inevitably builds up again over time, so the same job doesn't need repeating in two years.
Real Reviews For This Job
“Sam worked efficiently and cleanly. He arrived on time, protected the area around his workspace, and did a great job at a very fair price. Sam also services our boiler annually, and has always provided an excellent and professional service.”
Checkatrade member since March 2015, backed by their £1,000 guarantee.
Power Flushing & System Cleaning: The Questions People Ask
How do I know if I actually need a power flush?+
Cold patches at the bottom of radiators, a system that's noisy, or radiators that need bleeding constantly are the usual signs. Worth a water test to confirm before committing to one.
Will it fix a boiler that's already making noise?+
Often, yes, if the noise is caused by sludge (kettling) rather than a mechanical fault. That gets confirmed before recommending a flush as the fix.
How often does a system need flushing?+
Not on a fixed schedule the way a boiler service is. It's done when the symptoms point to it, or before a new boiler goes onto an older system.
Does a magnetic filter really make a difference?+
Yes, it catches the sludge that continues to form after a flush, which is the main reason a flushed system stays clean for longer instead of sludging up again within a year or two.