Engineers go underground in Liverpool city centre to shift a massive concrete slab that is reducing the sewer flow. Rookie waste-water engineer Bunty unblocks a stinking drain.

Two miles off the coast of Blackpool, specialist divers are on an underwater mission to clean a massive submerged outfall pipe that disperses treated wastewater deep into the sea. Water tester Annette is out in harsh Cumbrian weather to perform vital checks on the water quality in her area and sewage supremos Mick and Ash race to the aid of a family whose backyard is swimming with sewage from a bunged-up manhole.