Outside the back of the kitchen, there's a deepish gulley into which various drains empty.
It's about a foot deep right now. Soddit.
The bottom of the gulley opens onto the top of a drainpipe - which clearly isn't flowing anything like properly.
I've borrowed some drain rods off a neighbour, but just can't get 'em into the drain. I can't reach down enough to guide it manually.
Any thoughts?