Full system power flush, 1970s semi

The customer rang us in because three of the upstairs radiators weren't getting properly hot and the boiler had developed a noise they described as "like a kettle in the wall". Classic sludge symptoms in an older system — magnetite buildup choking the flow, cold spots forming in the rads furthest from the boiler.

I spent half an hour with a thermal imaging camera before doing anything — let the customer see exactly what was happening. The downstairs lounge rad was a clear band of hot at the top fading to stone-cold at the bottom. The hallway rad was barely warming up at all.

Magnacleanse chemical flush across the whole system, magnetic filter installed in line with the return, fresh dose of Sentinel X100 inhibitor. One radiator was beyond saving once we'd flushed it (a 1970s pressed-steel that'd been crusted shut at the bottom) and was swapped for a modern equivalent.

The downstairs loop also had a partial blockage from old jointing compound — cleared with a targeted reverse flush rather than a full strip-out. Final test: system ran 4°C hotter at the boiler return than before, no more kettling, all rads properly hot end to end. Customer should see the difference on next month's gas bill too.