Will it work? What are the dangers?

[roverbarmy]

Take off both rubber hoses. Pour in via highest hose using a funnel until it starts to leak out of lower hose. Lift each hose in turn to move descaler back and forth. Plug ends of hoses with a cork and leave to stand as long as you dare! Drain into a plastic bowl from lowest pipe. Backflush with water via a hose pipe. Refill and bleed system to test. Save the drained descaler/flush in case it needs another session. ( I hasten to add that I have never done this on a Rover but have done it on several other vehicles to good effect.)