I’ve not come across a blocked downpipe I’ve not been able to suck clear.
Gravity normally clears the vertical pipe, but all sorts of gutter junk can block the opening where the downpipe meets the roof gutter.
These photos are from an industrial unit. Extra wide and extra deep compared to domestic gutters because all that rainwater that lands on the big roof has to go somewhere.
Two thoroughly blocked downpipes meant that the water was overflowing at the lowest point of the run, unfortunately that was over the doors.
I sucked over 300 litres of leaf litter and standing water out and customer just reported that the gutters are no longer overflowing and water is running freely as it should.
Customer comment: ‘.. made a massive difference to our gutters, we would have been overflowing in this weather’