I often wonder whether there should be a different title to differentiate between a plumber who can fit pipes and one who can solve heating problems. (However, having heard of some problems at a new old people's home I wonder if some plumbers have never read the instructions on how to assemble plastic pipe joints. It is costing thousands to expose and chack all joints after several failed.)
I was speaking to a plumber about my heating. Whilst I can get a good full bore flow out of one of the radiator pipes - the other is merely a trickle. I feel it is a blockage at the microbore manifold)
The plumber told me that the one that trickled would be the return pipe and water isn't meant to flew from it!. I thought of drawing a diagram and explaining static pressure - but decided to play the thick punter and nod.