Thank you very much En. Rosman for such a helpful tips. I have exactly the same problem with my WC - Johnson Suisse, it normally occur when there is no water supply (tank empty).
Good informative video which is the first I've seen regarding a 'Back to the Wall - Close Coupled' toilet type cistern which is similar to the one installed by my bathroom contractors who left no instructions for maintenance such as replacing the fill valve or the syphon valve. Handy having the toilet in a wet room - ours is in an upstairs bathroom with wooden floorboards so a hidden leak would be a big problem.
Good video, clear and instructive. However the cause of the slow water is a bit puzzling..... water lock? I am also not sure about the back flushing solution....as the source of water for both would be from a common line....typically.
