How to drain down a central heating system | chemical flush

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Published Feb 20, 2023

In this video we are draining down a sealed central heating system, which is often found with combination boilers. The water in this system is filthy and needed replacing as soon as possible. It’s critical that the water in the central heating system is kept clean and free from iron oxide/rust/corrosion or limescale, as these things can cause severe damage to the system and the boiler. To do a job like this, it is going to take several hours, so it’s best to have everything ready in advance and be prepared to spend the whole day doing this job.

Sentinel X 800 was used as a chemical flush for the system, because the original water was completely black (it looked like used engine oil). This was left in the system for 1 hour, with the central heating switched on. This was then drained out, and the system was re-filled again, this time a central heating inhibitor, sentinel X100 was added to the system.