A blocked toilet, sink, bath or shower is where most drainage problems are first noticed, but it is rarely where the problem sits. Internal waste pipes are small bore, 32mm to 50mm on a sink, 110mm on a toilet, and they feed into a soil stack or a branch run that carries everything to the drain outside. A blockage can be in the trap under the fixture, in the branch behind the wall, in the stack, or in the below-ground run beyond the building.
We work the problem from the fixture backwards. Which fixtures are affected tells us how far down the system the obstruction is: one slow sink is local, a toilet and a shower backing up together is a shared branch, and everything on the ground floor rising at once is a below-ground run. That saves lifting floorboards for something sitting in a chamber outside.
Clearance is then matched to the pipe. Small-bore waste runs take mechanical clearance and flushing. Soil stacks and 110mm branches take rodding or controlled jetting. Below-ground runs get the CCTV camera and the full drainage treatment. Sheeting goes down, waste is vacuumed rather than mopped, and the bathroom or kitchen is left usable.