Microbore Central Heating Blockage Jun 2026

Furthermore, the blockage is rarely pure sludge. It is a composite material: magnetite particles bind with limescale (calcium carbonate) in hard water areas and with flux residues left over from the original installation. When a system is repeatedly turned on and off, the sludge undergoes thermal cycling, hardening into a cement-like substance known as “copper carbonate” or simply “hard sludge.” This metamorphosis transforms a removable deposit into a near-permanent obstruction that can withstand pressures of up to 3 bar.

In a microbore system, power flushing can be catastrophic. High-pressure water can dislodge a large "slug" of sludge in the main trunk, pushing it into the microbore tails. Because the tails are so narrow, the slug acts like a cork, completely blocking the pipe. microbore central heating blockage