Blocked Microbore -

The primary culprit in almost all heating blockages is "sludge." This is a black, mud-like substance (Magnetite) created when water reacts with the iron inside steel radiators and copper pipework.

Chemical inhibitors and sludge removers can be added to the system water. While effective for minor sludge buildup, they cannot dissolve a solid, hard blockage of hardened limescale or compacted magnetite inside a microbore pipe. blocked microbore