What Is Magnetite Sludge?
Magnetite is iron oxide (rust) that forms when unprotected metal components in the heating system corrode. It circulates as a fine black sludge throughout the system, blocking radiators, damaging the pump, and coating heat exchangers — reducing efficiency and causing premature failure.
Signs Your System Has Sludge
- Some radiators cold at the bottom (sludge blocking them)
- Boiler/heat pump making pumping noises
- Black, murky water when bleeding radiators
- System requires frequent repressurising
Powerflush Process
A powerflush uses a high-velocity, low-pressure pump to circulate water and cleaning chemicals through the system, dislodging and removing sludge. A magnetic filter removes particles. System inhibitor is added to prevent recurrence.
Cost
£300–£600 for a typical 3-bedroom home. Well worth it before a new heat pump installation if the existing system has sludge contamination.
Magnetic Filters
A magnetic system filter (e.g., Fernox TF1, Adey MagnaClean) should be fitted to all heat pump systems to capture future magnetite before it causes damage. Essential for any system that has had sludge issues.
Sources: the MCS scheme and aroTHERM plus specifications.
