Raw sewage was left running through Helston town centre on Friday after escaping through a drain cover.
The effluent left a large area of pavement below the entrance to the former Meneage Hospital off Meneage Street, now converted into flats, covered in excrement and waste paper.
The smell permeated the air from some distance, particularly downwind.
Pauline Wills, who lives just down the road, came across the unpleasant discovery shortly before 5pm while walking her dog. She said: “I could smell the smell. It was awful. It just made me feel quite sick.”
Mrs Wills contacted South West Water as “no one seemed to be doing anything about it”.
It is not the first time that the drain has overflowed, although never this badly before.
“It happened last year. They must have a problem there,” said Mrs Wills.
A spokesperson for South West Water said: “We received a report of a sewage leak in Meneage Street at around 5pm on Friday and attended within an hour-and-a-half to clear a blockage of silt and stone. Our crews also cleaned up the area.”