Full System Power Flush — Primrose Hill

The pattern is frustratingly common in London's Victorian housing stock. Heating performance declines gradually — so gradually that homeowners adapt to it before they identify it as a problem. Rooms that used to warm quickly now take twice as long. Radiators on the upper floors never quite get as hot as the ones downstairs. The boiler runs more than it used to, but the house feels no warmer.

The family in this six-bedroom Victorian terraced house in Primrose Hill had been living with exactly this for two winters. They'd had the boiler serviced the previous autumn by another company, who had declared it "working fine" and issued a certificate. What the other company hadn't done was test the water quality — which would have immediately told them that "working fine" was relative. The boiler was firing. The heating system was not working fine at all.

When RARE's engineer visited for an assessment, the water quality test result was visually striking: the sample drawn from the system was almost black. Severe magnetite contamination — the iron oxide sludge that accumulates in unprotected systems — was present throughout the primary circuit. It was coating the insides of radiators, partially blocking the narrow return pipework, and forcing the boiler to work significantly harder than it should to circulate water around the system.

The property had 16 radiators across four floors, with the original gravity-fed pipe layout still in place from the Victorian era. Some of the return pipework was 22mm copper — narrow enough that even moderate sludge deposits create significant flow restriction. Four of the radiators, particularly on the upper floors, were worst affected: they were barely warm even with the boiler running at full output.

RARE carried out a full MagnaCleanse power flush using a Kamco CF90 machine — the professional standard for heavily contaminated systems. The process began with a pre-flush water quality test to document the contamination level, which formed part of the written certificate issued on completion.

Each of the 16 radiators was flushed individually, with the machine cycling between forward and reverse flow to dislodge deposits from within the radiator body. The four most severely affected radiators — where sludge had impacted to the point of significantly restricting flow — were removed from the wall and flushed externally using a dedicated radiator flushing tool, which is the only reliable method for clearing heavy deposits from radiator cores without damaging them.

As each radiator was cleared, the water running through the machine changed from the initial near-black to progressively cleaner. By mid-afternoon, the machine was running clear on every circuit. A Fernox TF1 Omega magnetic filter was fitted to the boiler return — this will catch any residual particles and prevent any future contamination from accumulating. The system was dosed with Fernox F1 inhibitor to the correct concentration for the system volume, re-pressurised, and balanced: each radiator's lockshield valve adjusted to ensure even heat distribution across all four floors.

By 6pm, every radiator in the house was hot. The difference, the homeowners said, was extraordinary.