![Heating systems in apartment buildings and homes circulate water through pipes, radiators, and heat exchangers. Over time, corrosion inside the system produces sludge known as magnetite. This black sludge can significantly reduce heating performance. How Sludge Forms Sludge forms when oxygen in the water reacts with metal components inside the heating system. This corrosion produces […]](https://spcdn.shortpixel.ai/spio/ret_img,q_cdnize,to_webp,s_webp/sp-ao.shortpixel.ai/client/to_webp,q_lossless,ret_img/lhe.london/wp-content/uploads/2026/03/Clogged-HIU-filter-with-debris-1024x600.png "The Hidden Damage Caused by Sludge in Heating Systems")
Heating systems in apartment buildings and homes circulate water through pipes, radiators, and heat exchangers. Over time, corrosion inside the system produces sludge known as magnetite. This black sludge can significantly reduce heating performance.
How Sludge Forms
Sludge forms when oxygen in the water reacts with metal components inside the heating system. This corrosion produces magnetite particles that circulate through the system.
Common sources include:
• old radiators
• steel pipework
• untreated system water
• lack of inhibitor chemicals
Problems Caused by Sludge
Sludge can cause:
• blocked plate heat exchangers in HIUs
No heating and hot water
• poor radiator performance
• underfloor heating circulation problems
• pump failures
• noisy heating systems
In severe cases, entire heating circuits can become restricted.
How Engineers Prevent Sludge
Professional heating engineers prevent sludge problems by:
• flushing heating systems
• installing magnetic filters
• adding corrosion inhibitors
• maintaining system water quality
These steps protect sensitive components such as HIU heat exchangers.
If your heating system is suffering from poor performance, sludge may be the cause. Our engineers can inspect, flush, and protect your heating system to restore efficiency. Simply click here to book an appointment.
