Silly question: should downpipes be screwed together?

[voiceofthemysteron]

All pipe fittings should be push fit only and be allowed to overflow in case of blockage.You would not want the whole gutter system filling with water and overflowing.That's what i was taught in my apprenticeship in the 70's when i spent what seemed like forever fitting RWP on the largest housing estate in Europe at the time.

 

[noseall]

All pipe fittings should be push fit only

I agree with this but from an ex-con point of view.

Self drilling screws can be unscrewed as well as screwed.