The pump direction is determined by the winding sense of the main and start windings in the pump so i dont see how you think you are getting it to rotate in the opposite direction.
Furthermore in a boiler with a built in pump it becomes even odder!
Tony
what you dont know how to change the direstion of rotation in a single phase motor
if you turn the pump you aint changing the direction of rotation
just the flow
sounds off to me
but TBF never tryed it
worst boiler i ever had for an airlock was a sine 18 (you younguns get your history books out)