If a system is not properly flushed before commissioning, or if repairs are conducted without cleaning the pipes, flux residues, copper filings, and solder can remain in the system. These solids can lodge in filters or pipe bends, causing immediate or long-term obstructions.
After the powerflush, I had them install: blocked central heating pipes
The most prevalent cause of blockages is "sludge," a thick, black or brown mud-like substance. This forms when water reacts with the iron inside steel radiators, a process accelerated by the introduction of fresh oxygen through leaks or improper maintenance. As the metal corrodes, the resulting debris circulates and settles in the lowest points of the system or inside narrow pipes. If a system is not properly flushed before
£850 powerflush + £150 pipe replacement. Alternative cost if I’d ignored it: A new boiler (£3k+) when the heat exchanger cracked from the pressure. This forms when water reacts with the iron
The majority of blockages in central heating systems are not caused by external debris, but by internal chemical reactions and biological growth.