firstly,nice manicured finger nails for a window cleaner

not knowing the lay out of the piping system i would take the view that the non return valve is not going to do any harm being there.
as sponge bob said it is a bit ott for a garage,so if you did remove it you could fit an isolating valve and this would allow you too isolate the system from the rest of the layout when needed
non return valves are used to stop cross contamination,ie hot water into cold etc
as for the 22 mm you would not gain much