[Roanon]

The knwoledge about a good sewer system was lost in the dark age, as several other comforts that we consider to be modern.

Most sewer systems fell into disrepair some time after the fall of the Roman empire and were never repaired. Christian church and its inquisition ruled and nobody dared to be too modern or inventive. Letting the sewage flow freely into rivers and lakes was common, and middle-age citys usually radiated a penetrating stench so that you could smell any city before you could see it.

The contaminated water often caused mass diseases like cholera and thypus when a city grew too much, keeping the cities small. And it led to the (in these times partially correct) opinion that water was generally unhealty, leading to the noble's habit to use powder and perfume rather than washing with water.